LOS ANGELES:China's Zheng Jie engineered a stunning upset of World No 1 Dinara Safina 7-5, 4-6, 6-4 in the third round of the WTA Los Angeles Tennis Championship on Thursday.

With the victory the 26-year-old from Cheng Du highlighted a bruising fourth day for the top seeds at the $700,000 hardcourt event. Zheng also snapped a four-match losing streak to Safina dating back to 2005 when they met in the early rounds of the Australian Open. Safina also won matches at last year's French Open and the Beijing Olympics and another three setter earlier this year on the clay in Rome.

Zheng improves to 21-15 in 2009 as she seeks her fourth career WTA title. Zheng, who is ranked 23rd in the world, made 77 per cent of her first serves and had just one double fault in the two hour, 10 minute match on centre court.

It was one of three upsets of top ranked players on Thursday as former World No 1 Ana Ivanovic and fifth seed Nadia Petrova were also ousted. The 10th-seeded Flavia Pennetta upset Russian Petrova 6-3, 6-3. Another upset came when 13th-seeded Aussie Samantha Stosur beat Ivanovic 6-3, 6-2. Serbia's Ivanovic was seeded sixth and is a former French Open champ. Zheng and Stosur will meet in the quarter-finals.

In other matches, Russian Vera Zvonareva outlasted Yanina Wickmayer 7-6 (7/5), 4-6, 6-4. The second seeded Zvonareva, who lost in last year's final, will next face Pennetta at The Home Depot Centre facility in south central Los Angeles.

Also, eighth-seeded Agnieszka Radwanska, of Poland, breezed past Russian Anna Chakvetadze 6-3, 6-2 and Russian Maria Sharapova defeated Alona Bondarenko of the Ukraine 4-6, 6-0, 6-3.

A couple of injuries came into play as China's Li Na withdrew from her third-round match against Poland's Urszula Radwanska due to a right knee injury. Also, Sorana Cirstea was ahead 6-3, 1-0 on Sabine Lisicki when the German retired because of a shoulder problem.