Kvitova, Sharapova advance in Melbourne

MELBOURNE, Jan. 21 (UPI) -- Petra Kvitova, seeking her second title in her last three grand slam appearances, breezed into the fourth round Saturday at the Australian Open.

Kvitova, the No. 2 seed, advanced when Maria Kirilenko retired in the second set with a thigh injury. Kvitova had a 6-0, 1-0 lead at the time and now will meet Ana Ivanovic in the round of 16.

Ivanovic ended the run of American Vania King 6-3, 6-4.

Kvitova broke through with a championship last summer at Wimbledon and then lost in the first round of the U.S. Open. She remained on course for a semifinal meeting in Melbourne with fourth-seeded Maria Sharapova, who reached the fourth round Saturday with a 6-1, 6-2 decision over Angelique Kerber.

In the day's biggest upset, Ekaterina Makarova ousted No. 7 seed Vera Zvonareva 7-6 (9-7), 6-1.

Other third-round matches saw Sara Errani defeat Sorana Cirstea 6-7 (6-8), 6-0, 6-2 and Zheng Jie defeat Marion Bartoli 6-3, 6-3.

Serena Williams was scheduled for a night match against Greta Arn.