Farhan Shakor then restored Iraq's lead just before the break, but a Lee Gwanghun strike restored parity and forced extra time.
Farhan thought that he had given his side the win with a 119th minute strike in extra time, but Jung Hyuncheol scored with the last kick of the match to take the game to penalties.
Lee Gwanghun missed an all-important spot kick in sudden death, allowing Farhan to play the part of hero again by scoring the winning penalty.
You can read how a dramatic 90 minutes unfolded with Sports Mole's live play by play coverage below.
3.30pmGood afternoon! Thank you for joining Sports Mole for today's first Under-20 World Cup quarter-final match as Iraq take on South Korea. Both sides have done brilliantly to reach the last eight, and for one of these underdogs it will get even better as they are playing for a place in Wednesday's semi-final.
3.32pmWe'll start by looking at Iraq, who have been arguably the most surprisingly impressive team in the tournament so far. They are still unbeaten in the tournament, which is something that no other side still in it can say.
3.34pmIt's not like they have had an easy passage through either. There were tougher groups than the one they qualified from, but to finish top of the pile with the likes of England, Chile and Egypt in your group is a big achievement.
3.36pmIraq managed a fine 2-2 draw with England in their opening match before consecutive 2-1 wins against Egypt and Chile respectively. They followed this up with a 1-0 win over Paraguay in the first of the knockout rounds, although they did need extra time on that occasion.
3.38pmThey are in the last eight on merit, there is no doubt about that. The exploits of these young players could point to a bright football future for a country that has experienced such turmoil in their recent history.
3.40pmIt's not all good news for Iraq today, however. They will be without talisman Mohanad Abdulraheem due to an amalgamation of yellow cards over the previous games. There is no doubt that he will be a huge loss for the Iraqis. The attacker was named AFC Young Player of the Year last season, so his absence would hurt any side.
3.42pmMoving our attention to Korea, their passage through the tournament hasn't been quite as impressive as Iraq's. They needed a dramatic penalty shootout, which ended 8-7, to see off Colombia in the last round, while they only managed a third-place finish in their group.
3.44pmThey kicked off their campaign with a 2-1 win over Cuba before drawing 2-2 with a much-fancied Portuguese side. A 1-0 defeat at the hands of Nigeria saw them drop to third in the group, but their tally of four points was enough to see them through to the knockout rounds.
3.46pmWhile Korea may not have been as eye-catching as Iraq in the current tournament, the last time these two teams met it was Korea who had the last laugh. They came back from a goal down to beat Iraq on penalties in the Under-19 Asian final.
3.48pmThe defeat clearly still hurts Iraq. Their coach, Hakeem Shakir, has already said that this "will be a revenge match for us".
3.50pmShakir went on to say: "They took the cup from us at the Asian Championships but now we want to show who's best in Asia in front of the whole world. We were unlucky last time but on this occasion we are ready to be more precise in our play, and to win for sure. I will say now that this Iraqi team can go all the way to the final."
3.52pmBig words from Shakir, then, who is clearly backing his side, and why not? They have already done more than most people expected. A semi-final against Uruguay awaits the victors of this one, which is by no means an easy test, but anything can happen in the semi-finals of a competition.
3.54pmOne of Iraq's biggest strengths so far this tournament has been their never-say-die attitude. They have scored four of their seven goals on the 75th minute mark or later.
3.55pmPREDICTION: We're five minutes from kickoff in Turkey, which means that it is time for my match prediction. With two teams who are usually underdogs facing each other, one side will be in the unfamiliar position of being favourites. That is probably Iraq on current form, but I think that they will be able to cope with that and I'm going for a 2-1 Iraq win this afternoon.
3.57pmOne area that Iraq have struggled with is the lack of a prolific goalscorer. Their seven goals have been spread out throughout the squad with no player managing more than one goal.
3.59pmSouth Korea, meanwhile, have scored the fewest goals of any of the sides who reached the quarter-finals. Ryu Seungwoo is their top scorer of the tournament with two goals to his name, but he is injured today.
4pmThe players are just in their huddles now, firing themselves up for the last time before this one gets underway. A place in the last four awaits one of these sides.
0 minKICKOFF: Here we go! Korea kick us off in the third quarter-final of the Under-20 World Cup.
1 minKorea come forward early on with a quick break as Arebat rolls on the floor apparently injured. Korea refuse to put the ball out of play but their attack eventually peters out and Iraq have a goalkick.
3 minBoth sides are just sizing each other up at the moment, it has been a slow start. Iraq have seen more of the ball, but we are still in the very early stages of this match.
5 minIraq have tried a number of long, high balls towards their strikers in the opening exchanges, but none of them have come off yet. The Korean defence isn't exactly a towering aerial presence, but they have dealt with any danger very comfortable so far.
6 minCHANCE! The first opening of the match falls to Iraq as Farhan Shakor gets the wrong side of the defence. He pokes the ball goalwards just before the Korean defence can get back with a sliding tackle, but Lee is out to save well from a tight angle.
8 minThere is a decent atmosphere inside the ground for this match, with the Iraqi fans making most of the noise at the moment. Their side's exploits have been a source of great pride to the fans.
10 minCHANCE! Korea's best chance of the match so far is thwarted by some last-gasp defending from Iraq. Han came forward and found space on the edge of the box before feeding the ball into the path of Kwon, who played a first time pass to Kim. The Korean striker took a touch before trying to steer it into the bottom corner, but a combination of two Iraqi defenders got back to deflect it behind for a corner.
12 minBoth sides are defending with plenty of bodies behind the ball, which leaves their attackers isolated when they gain possession. However, both sides are also looking to break quickly and attack in numbers when the chance presents itself.
14 minIt has been a very even opening quarter of an hour or so. Each side has had one decent sight of goal each and look capable of creating something every time they come forward.
16 minShakor goes down theatrically but wins a free kick for his side in a good crossing position. This is a good chance for Iraq as their defenders trot forward into the Korean box...
17 minCLOSE! Ali Adnan fizzes a fine free kick right across the face of goal and all it needs is a touch from one of the three Iraq players who are attacking the ball, but none of them can reach it!
21 minIraq take the lead in this quarter-final! The initial penalty decision looked a little soft, but after seeing the replay the referee had no choice. Kim surpasses the usual hustle and bustle in the penalty area from a free kick by pretty much rugby tackling Ali Adnan to the floor. The Korean striker picks up a yellow card for his troubles, but even worse for them Ali Faez stepped up and made no mistake with his spot kick, sending the keeper the wrong way.
25 minI was just about to ask how South Korea were going to react to going behind, but they've answered the question already. It is dreadful defending from Iraq as a long throw by Sim finds Kwon completely unmarked inside the box. He is one of the smallest players on the pitch but he rises unchallenged to nod the ball past the keeper. Game on!
27 minIraq will be livid with themselves at letting such a weak goal in so soon after going ahead. They need to do it all again now.
29 minIraq have responded pretty well to that quick equaliser. They have reclaimed possession of the ball and are knocking it about nicely, killing any momentum that Korea may have built up with that goal.
30 minSHOT! Ali Adnan has been impressive so far this afternoon, and he almost gives Iraq their lead back. He gets past three Korean defenders before advancing into the box and flashing a decent effort just past the far post.
32 minIt has been an even opening half hour or so. Both sides are looking to play good, attacking football and it is an entertaining match to watch. I can see more goals in this one, but at the moment a draw is probably the fairest scoreline.
34 minHaving said that, Iraq have certainly been the better team since that equaliser. They are enjoying plenty of the ball inside the Korean half and have threatened a few times from in and around the edge of the area.
36 minOf course, as soon as I say that Korea begin to come back into it themselves. They now have a corner after Saif was forced to bundle a low cross behind.
37 minThe corner reaches Lee at the back post, and he tees up Han whose effort is deflected just wide for another corner, which is cleared by Iraq.
38 minYELLOW CARD! Iraq pick up their first yellow card as Nadhim comes right through the back of Kim with a poor challenge. Correct decision by the referee.
40 minFarhan is down hurt at the moment but he should be able to continue. He fell awkwardly when going up for a header and appears to have hurt his lower back. The other players take the opportunity to have a quick drink in this scorching heat.
43 minIraq regain the lead just before half time! A diagonal ball into the box finds Ali Qasim, who produces a sublime volley with the outside of his boot when off balance. Lee pulls off an equally impressive save, but he can only parry it into the path of Farhan, who fires it into the roof of the empty net.
44 minYELLOW CARD! Kang Sangwoo picks up a yellow for a blatant pull on an Iraqi player. That means that he will miss the semi-final, should Korea make it there.
45 minKOREA SUB: He will also miss the rest of this match as he is immediately subbed after that yellow card to be replaced by Lee Gwanghun. That is an attacking sub by Lee Kwang Jong.
45 minThere will be two minutes of added time here.
4.50pmThe referee brings an end to a thoroughly entertaining half of football, and it is Iraq who will go in to the changing rooms happiest. They lead South Korea 2-1 at the break thanks to a Farhan strike just two minutes before the whistle.
4.52pmThe scoreline is probably just about a fair reflection on that first half. It was very even for large parts of the opening 45 minutes but, if any deserves to be winning, it is Iraq. They have presented more of an attacking threat than Korea.
4.54pmThe opening goal came from the penalty spot after Kim Hyun had hauled Ali Adnan down inside the box when attempting to defend a free kick. Ali Faez made no mistake, but Iraq were only ahead for a matter of minutes as Kwon Changhoon nodded Korea back level almost immediately.
4.56pmThen, just before the break, Farhan Shakor did what any good striker should do and followed in a teammate's shot. He was rewarded as Lee's fine fingertip save fell straight to his feet and, although he seemed to do everything he could to blaze the chance over, he managed to convert his effort.
4.58pmA quick reminder of exactly what these two sides are playing for: The winners will reach the semi-finals of the Under-20 World Cup to face Uruguay, who produced a major shock yesterday by beating tournament favourites Spain.
5pmAlso yesterday, France hammered Uzbekistan 4-0 to reach the semi-finals, where they will face either Ghana or Chile. Those two face each other later today, and you can follow that match live with Sports Mole too. Coverage will start at 6.30pm ready for a 7pm kickoff.
5.02pmThe players are just about to come back out ahead of a huge next 45 minutes. For Iraq, they are on the verge of getting further in this tournament then they have ever managed before. For Korea, they need a goal to remain in the competition.
45 minKICKOFF: We're back underway here, Iraq restart the match. Can they hold out or even extend their lead in the next 45 minutes?
46 minKorea have made a fast start to this half and Han is almost released through on goal but the pass is ever so slightly behind him, allowing the Iraq defence to get back and hack the ball clear.
48 minYELLOW CARD! Saif picks up a yellow card for a rash sliding challenge on Kim Yonghwan. The ball appeared to be out of reach of the Korean full-back but it was still a bad tackle the ref made the right decision. Free kick in a good crossing position for Korea here...
50 minKorea equalise again, and again it is poor aerial defending from Iraq. The delivery from the free kick was good, but no-one followed Lee to the near post and he simply flicked his header in. The keeper seemed to flinch and turn his back on the ball rather than trying to save it. Poor, statuesque defending all round, and I'm especially baffled as to what Fahad Talib was doing in goal for Iraq!
52 minCHANCE! Iraq just haven't got started in this second half yet, it is all Korea. They probably should be in front for the first time today there as another high ball causes havoc for Iraq. Kim Hyun easily wins the header, nodding it into the path of Kwon who blazes his effort well over when he should have scored. Big chance.
54 minIraq are finally starting to look like they did in the first half now. Abdulhussein makes his way to the byline but can't pull it back enough as his cross clams into the side netting. Korea will be eager to exploit the obvious weakness that Iraq have in defending aerial balls, though.
56 minIt has been a very strong response to that goal from Iraq. They still look very dangerous when they come forward and I will be surprised if we've seen the last of the goals in this one.
59 minLee fails to hold on to a powerful free kick from Faez as it bounces just in front of him. Those are always hard to hold on to and Lee did fairly well to shovel it away and out of danger.
62 minMahdi races down the right flank and sends a ball towards Tareq, who is racing through the middle unmarked. The pass is just too heavy, however, and Tareq is forced out wide before sending a cross into the arms of Lee. That would have been a good chance if Mahdi could have got the pass right.
64 minFarhan is down once again, this time holding the side of his head after what seemed like an innocuous coming together. The Iraqi striker seems to go down fairly easily it must been said.
66 minA long ball upfield breaks for Lee Gwanghun on the right side of the box, but he is forced a little wide for his liking and his eventual shot from a tight angle lacks the power to cause the keeper any troubles.
68 minIRAQ SUB: Iraq make their first change of the day as Mohammed Jabbar Shwkan comes on for Ali Qasim.
70 minThe game has struck a bit of a lull in the last 10 minutes or so. Neither side wants to lose this one now, which has ensured that neither are attacking as freely as they were earlier in the match.
72 minThe passes in the final third are just not coming off for either side at the moment. Nerves are beginning to creep in as we approach the final 15 minutes. Remember that Iraq have scored four goals after the 75 minute mark in this tournament so far, they are late goal specialists.
74 minAs things stand we will be going into extra time and perhaps penalties. Both sides were forced into extra time in their last matches, while Korea needed to go all the way to penalties before eventually qualifying. Will tiredness play a factor in the last 15 minutes?
76 minSHOT! An increasingly rare effort on goal from either side sees an off-balance Shwkan curl a shot towards the top corner. It's a decent attempt from the sub, but he can't keep it down and it flies a couple of yards over the bar.
78 minIt is Iraq who are starting to pile the pressure on. Korea don't have a single player in the Iraq half at the moment, and they look content to take this match to extra time.
80 minWhereas both sides looked dangerous every time they came forward earlier, neither side really look like scoring at the moment. The game should get more stretched in these final 10 minutes, however, which will hopefully provide a few more chances.
82 minKorea have just edged the possession in this one, enjoying 51% of the ball to Iraq's 49%. It has been a close contest throughout and a draw would be a fair result after 90 minutes. It can't end that way, though. We must have a winner today, be it via 90 minutes, extra time or penalties.
84 minTareq is penalised for a high foot and Korea now have a free kick in a good position. They are slightly to the left of centre around 30 yards from goal. It is just within shooting distance, but it would have to be some strike to score from here.
86 minThere are handbags in the wall as Kim slightly raises his arms towards an Iraq player, who goes down like he has been shot. Ridiculous piece of diving there.
87 minSHOT! Kwon lines up the free kick but his eventual effort is never troubling the Iraq goal. He gets it over the wall but can't get it back down in time as it curls comfortably over the bar.
89 minAny goal now would surely be a winner for either side, although it must be said that they look resigned to extra time already.
89 minDecent chance for Korea here, however, as they have a free kick in a good crossing position. Iraq have struggled to deal with crosses into the box so far today...
90 minMohammed Hameed has looked shaky under the high ball at times today but he gets a vital fist to that ball and punches it clear.
90 minThere will be three minutes of added time here. Can either side grab a dramatic late winner?
90+2 minAli Adnan has been impressive today and the full-back is still full of running as he makes his way down the left flank. He is well marshalled, though, and sees his cross blocked.
90+2 minNow that would have been some way to decide this match. Farhan takes the ball down on his chest before producing a bicycle kick from outside the box that is quite awkward for Lee to gather.
5.55pmSo it is a second consecutive extra time period for both of these sides as 90 minutes could not separate them. It has been a largely entertaining match, even if it did peter off a little towards the end. Tiredness will now surely play a part as we face another 30 minutes of football at least.
5.57pmGoals from Ali Faez, Kwon Changhoon, Farhan Shakor and Lee Gwanghun has got us to where we are now. It has been an even game overall, and neither side really deserves to be eliminated from this one.
90 min ETKICKOFF: We're back underway once again here in Turkey after a brief stoppage. We have at least 30 more minutes of football ahead of us.
92 min ETIRAQ SUB: Iraq make their second sub of the game as Abdulhussein makes way for Jawad Kadhim.
94 min ETSubstitutions could have a big impact in extra time here. Neither side used their three allotted subs in normal time, so there are plenty of fresh legs waiting to come on and make a difference.
96 min ETCHANCE! Big, big chance for Korea! Han cuts the ball back into the box and Korea's first shot is deflected into the path of Kwon right in front of goal. Just like in the second half, however, he snatches at his effort and balloons it over the bar when he should have scored. Really good chance, that.
98 min ETAdnan makes another determined run forward and he is only stopped by a foul around 35 yards from goal. It is too far to shoot, but it is a good chance for Iraq to float a cross in here...
99 min ETOFF THE LINE! The initial free kick comes to nothing, but Iraq get it back into the box and Tareq fires a shot goalwards on the turn. It beats the keeper, but Lee Changmin is waiting on the line to hack it clear. So close for Iraq!
100 min ETSAVE! Lee Changmin almost makes himself a hero at the other end as well! He is teed up from a free kick around 30 yards from goal and his powerful strike is swirling and moving around in the air. Hameed deals with it well, however, tipping it over the bar for a corner.
102 min ETKadhim makes a powerful run forward down the left flank before eventually winning a corner. As has been the case with the vast majority of high balls into the box for Iraq, however, it comes to nothing. Korea have certainly won the aerial battle this afternoon.
104 min ETA small misunderstanding between Hameed and his defence almost allows Korea in, but the keeper eventually comes out to collect the ball. That was a shaky moment for Iraq.
105 min ETCramp is setting in on a few of the players now, and it is no surprise. Both sets of players have gone the distance in their last two matches.
105 minThere will be just one minute of added time at the end of this first half of extra time.
6.15pmStill nothing to separate these two teams as the first half of extra time ends. The referee wants a quick change around but both sides are eager to have a little rest and take on some liquid.
6.16pmKOREA SUB: Lee Changmin, who cleared that effort off the line earlier, makes way for Woo Jusung, who is a defender by trade. Quite a defensive sub.
105 min ETKICKOFF: We're back underway for the final time this afternoon. Can either side find a winner in these final 15 minutes, or will we have a penalty shootout?
107 min ETThe ref sees a late flag from his assistant that awards Korea a free kick in a very good crossing position. That is how both of their goals have come so far, can they get another here?
109 min ETSAVE! Kwon tries to fool everybody by going for goal from the tight angle, and it is a very good effort. It almost catches Hameed off guard, but he responds well to get across and make the save.
111 min ETIraq concede another free kick in a good position for Korea to cross it in. This decision is a bit harsh, to be honest, but Korea have a good chance to put more pressure on Iraq here.
112 min ETIRAQ SUB: Before the free kick can be taken Iraq will make their final change. On comes Hozan Ismael, a senior Iraq international, to replace Mahdi Kamil.
113 min ETThe free kick is again curled towards goal, but this time it is a lot less threatening as it floats over the crossbar. It wasn't too far away, but the keeper had it covered anyway.
115 min ETAdnan has really impressed me this afternoon. He is still bombing down the left flank and is a tough player to stop when he gets going. It takes two Korean players to eventually take the ball off him on this occasion, but he relieves some of the pressure that had been building on Iraq.
117 min ETIraq are starting to put some pressure on now. They have been second best in this extra time period so far, but they are doing what's needed when it matters.
119 min ETGOAL! Iraq 3-2 South Korea (Farhan Shakor)
119 min ETWhat was I just saying?! The late goal specialists have done it again! That is surely the winner, and Iraq won't care one bit that it is one of the scrappiest goals of the tournament so far. A long throw was flicked on and dropped just in front of the keeper, where Farhan was waiting to flick it underneath Lee. It was Farhan who got the goal in extra time in the last round, and he is the hero again today!
120+2 min ETOh my word, what an end to this match! Iraq thought that had won it with just 15 seconds left on the clock! Jung has other ideas, though, as he let's fly from 30 yards. His effort deflects off an Iraqi defender which takes it past the keeper into the top corner. Huge drama here, and we will be going to penalties!
120+2 minEND OF EXTRA TIME: Iraq 3-3 South Korea - penalties to come
6.37pmWow. That was a breathtaking finish to what has been a thoroughly entertaining match. It's not over yet, not by a long shot. We will have the dreaded penalty shootout now. It's hell for fans of either side, but great drama for the neutrals!
6.39pmThe Iraqis are united in prayer ahead of this shootout. Can they put that last-gasp goal behind them and win this now? Remember, these two sides met in the U19 Asian Championships last season, and Korea won on penalties.
6.41pmKorea have also tasted penalties in this competition as well. They triumphed 8-7 over Colombia in the last round. You'd have to put them as favourites now.
6.41pmKorea will take the first penalty, and it will be Kim Sunwoo...
6.50pmThere you have it! Iraq are through to the semi-finals of the Under-20 World Cup, and the celebrations are wild! That's it from me in this match, be sure to check out the other quarter-final between Ghana and Chile, live coverage of which will begin in the next couple of minutes on Sports Mole.