Former world number one Martina Hingis powered into the quarter-finals of the $600,000 Qatar Open with a 6-1, 6-2 win over third seed Francesca Schiavone of Italy on Wednesday.

She was joined in the last eight by French top seed Amelie Mauresmo, who proved too strong for compatriot Marion Bartoli, winning 6-0, 6-2 in less than an hour.

The Australian Open champion will next meet Italian Roberta Vinci, who defeated Maria Vento-Kabchi 6-2, 6-3, while unseeded Hingis, winner of the inaugural edition of the tournament in 2001, faces former U.S. Open champion Svetlana Kuznetsova.

Sixth seed Kuznetsova went through with a 6-4, 7-6 triumph over fellow Russian Maria Kirilenko.

Hingis only returned to the tour at the start of the year after retiring in 2002.

"I am playing well and I am happy about it," the Swiss told reporters.

"I was serving 40-0 and held my serve in the first game which is an indication that everything is fine with my game.

"I want to play on and win tournaments, not just to get knocked out in the first or second round, " the 25-year-old added.

Seeds Anastasia Myskina of Russia and Slovakia's Daniela Hantuchova fell by the wayside.

Fourth seed Myskina was beaten 7-6, 6-7, 6-4 by Japan's Ai Sugiyama, while Hantuchova, seeded five, went down 4-6, 7-6, 6-1 to China's Li Na, who lost to the Slovakian in Dubai last week.

Sugiyama, ranked 26th in the world, now meets Germany's Julia Schruff.

"She (Sugiyama) was better than me today," Myskina told reporters.

"When I was trailing 4-5 in the third set I lost my serve. Had I held it, it could have been different."

Second seed Nadia Petrova of Russia had a 6-1, 6-2 win over Greek qualifier Eleni Daniilidou.