Serena Williams has 10 aces in victory

WIMBLEDON, England -- Four-time champion Serena Williams reached the fourth round Saturday at Wimbledon by beating 26th-seeded Maria Kirilenko of Russia 6-3, 6-2 with the help of 10 aces.

Williams picked up her first straight-set win in five matches since she returned this month after being away from the tour for nearly a year because of a series of health scares, including blood clots in her lungs.

Top-ranked Caroline Wozniacki and 2004 winner Maria Sharapova also won in straight sets to reach the round of 16.

Williams , seeded seventh, is trying to become the first woman since Steffi Graf in 1991-93 to win three consecutive titles at the All England Club.

Against Kirilenko, Williams saved the only break point she faced and put together a 32-9 edge in winners.

"The matches are getting better, my serve is getting better, so it's just getting the rhythm that I've been missing a little bit, and it's good," Williams said. "I just want to continue to serve better like I did today, and just hold on out there and just move, and just really more than anything enjoy myself and stay focused."

Williams will play 2007 Wimbledon runner-up Marion Bartoli, the ninth-seeded Frenchwoman who beat Flavia Pennetta 5-7, 6-4, 9-7.

Wozniacki, still looking for her first Grand Slam title, swept Jarmila Gajdosova 6-3, 6-2 to make the fourth round for the third straight year.

Wimbledon is the only major championship in which the Dane has not reached at least the quarterfinals.

Sharapova, the only champion in the women's draw other than the Williams sisters, struggled with her game but still progressed relatively easily against Klara Zakopalova of the Czech Republic, winning 6-2, 6-3.

The fifth-seeded Russian -- watched by her fiance, New Jersey Nets guard Sasha Vujacic -- had 21 unforced errors and four double-faults in an inconsistent baseline performance in the wind on Court 2.

But, after falling behind 3-1 in the second set, Sharapova lifted her game to win five games in a row to finish off the 35th-ranked Czech player.

Sharapova hasn't reached the semifinals since 2006. She will next face 20th-seeded Peng Shuai of China, who beat Melinda Czink of Hungary 6-2, 7-6 (5).

In other matches, sixth-seeded Francesca Schiavone, the 2010 French Open champion, lost to Tamira Paszek of Austria in a three-set marathon -- 3-6, 6-4, 11-9.

No. 18 Ana Ivanovic, a former top-ranked player and 2008 French Open champion, was knocked out by Petra Cetkovska, 6-2, 7-6 (0).

Information from The Associated Press was used in this report.