Defending champion Ana Ivanovic crashed out of the French Open as she lost in straight sets to Belarus' Victoria Azarenka on Suzanne Lenglen court.

Given that eighth seed Ivanovic had not lost a set in her run to the last 32, Azarenka's 6-2 6-3 win came as a surprise.

Ivanovic said: "I started really well and felt good in the beginning but after the first point of the fourth game, I just started feeling so dizzy and I completely lost my balance.

"After that, it was really hard. I struggled with looking up. But she played well."

Ninth seed Azarenka will take on top seed and title favourite Dinara Safina next.

Safina has dropped just five games in her march to the quarter-finals.

The world number one continued her imperious form on clay with a comprehensive 6-1 6-0 win over French hope Aravane Rezai.