Victoria Azarenka through after tough Michaella Kraijcek test

World number one Victoria Azarenka has booked her place in round three of the Sony Ericsson Open in Miami, Florida, with a hard-fought straight-sets win over Michaella Krajicek.

Azarenka looked to have taken the initiative in the first set with an early break of serve, but Kraijcek snatched a break of her own to level the proceedings.

Despite Kraijcek's fightback, the Belarusian showed all of the aggression that has seen her go unbeaten in 2012 to break back twice and take the set 6-3.

The 22-year-old gained the advantage early in the second when she broke Kraijcek to lead 4-2.

However, Kraijcek, who continued to battle away at the baseline, broke back twice as she took control to leave herself serving for the set.

As Azarenka looked like she was going to lose only her second set of 2012, she dug deep to break for a second time before a third saw her claim the set 7-5.