Soyuncu last month suggested that he was aware of interest from the Gunners, who are looking to bolster their defensive options under new manager Unai Emery.
The 22-year-old's representative Mustafa Dogru has now confirmed that negotiations have begun with Arsenal, but also revealed that three other Premier League clubs are among the interested parties.
"Sven Mislintat has been keen on Caglar since he was at Borussia Dortmund. He first scouted him back in Germany. Sven is interested in Caglar, there are concrete talks, all that remains is for a fee to be agreed. We will see what happens next," Dogru told Turkish Football.
"What I will say regarding the Liverpool link is that there were four to five Premier League clubs scouting him over the international break. There are four Premier League sides who've made a move for Soyuncu, that we are in talks with. There is also interest from Atletico Madrid in Spain and a few clubs in France, Italy and Germany.
"I'm not surprised by the interest, Caglar is a modern defender, he's mobile, fast, dual-footed, has an excellent passing range. He's also tough and very physical. I think the Premier League is ideal for a defender with his attributes. I think he is ready now for a new challenge but we will see what happens."
Freiburg are thought to be demanding around £35m for Soyuncu.