World number one Victoria Azarenka and second-ranked Serena Williams eased into the Qatar Open quarter-finals with dominant third-round victories on Thursday.

American Williams, the 15-times grand slam champion who could return to the top of the rankings if she wins the tournament, crushed Pole Urszula Radwanska 6-0 6-3.

Belarussian Azarenka, who won last month's Australian Open, demolished American Christina McHale 6-0 6-0 in just over an hour and Russian third seed Maria Sharapova overpowered Czech Klara Zakopalova 6-3 6-3.

"I felt like I came out very focused, with a good mindset and a good game plan," Azarenka said on the WTA website (www.wtatennis.com).

"There were a few close games, but I felt like I was really taking advantage of every opportunity I had and not letting her play her game," added the top seed who notched the sixth 6-0 6-0 win of her career.

Fourth seed Agnieszka Radwanska beat former world number one Ana Ivanovic 6-1 7-6 and will next face Caroline Wozniacki, another former world number one, who defeated German Mona Barthel 7-6 6-3.

"It wasn't great tennis out there today - the wind was a huge factor," Wozniacki said. "To be honest it was just about getting the ball in play today.

"I was just trying to get it in and hoping for the best. It was a struggle, but I got through it," added the Dane.

Australian Sam Stosur reached the last eight with a 6-4 7-5 win over Russian Svetlana Kuznetsova and sixth seed Sara Errani knocked out Slovakian Daniela Hantuchova 7-5 5-7 6-2.

Czech Petra Kvitova completed the quarter-final lineup after recovering from a slow start to overcome Russian Nadia Petrova 4-6 6-4 6-3.