Samantha Stosur's stunned world No. 1 Caroline Wozniacki 6-4, 6-3 at the WTA Championship in Doha on Wednesday, while Vera Zvonareva and Kim Clijsters also claimed group stage wins.

Australian Stosur had too much pace and power for baseline battler Wozniacki, who needs one more win in Doha to secure the year-end No. 1 one ranking.

Stosur opened her Maroon Group campaign on Tuesday with a straight sets win over French Open champion Francesca Schiavone and she produced another dominant display at the Khalifa Tennis Complex.

"Very happy overall with the whole match. Soon as I got a chance I took it," Stosur said.

"If you can beat a player like Caroline in straight sets here at such a big event, then it's fantastic. I've got obviously one more round match tomorrow, and hopefully I can find myself in the semis."

The first set went on serve until the 10th game when Stosur's relentless pressure paid off.

With Wozniacki's serve lacking her customary zip, Stosur pressed home the advantage and forced the Dane into a weak lob that she put away to win 6-4.

In the second set, Stosur continued to take the game to Wozniacki, who began to show signs of frustration.

The Danish 20-year-old had a glimmer of hope at 3-5 when Stosur double faulted twice, but the Australian held her nerve and closed out the set for the win.

Wozniacki, who steamrolled Elena Dementieva in her group opener, said Stosur had been an entirely different proposition.

"She was serving well definitely, and she's hitting with a lot of spin. She's playing different than the other girls," added the Dane.

"I didn't take my chances. I had a lot of breakpoints in the first set, I didn't take them. I just need to just try to get over it fast and then prepare for tomorrow."

Zvonareva, who could still snatch the world No. 1 ranking from Wozniacki, beat Victoria Azarenka 7-6, 6-4 to claim her second White Group win of the US$4.55 million tournament.

After an uninspired opening, punctuated by a bizarre breakdancing interlude on the purple-colored court following the second changeover, Zvonareva's superior groundstrokes began to tell as Azarenka became increasing erratic and emotional.

The 21-year-old from Belarus squandered a glorious chance to break in the eighth game, letting out a deafening shriek of frustration.

The first set went to a tiebreak, Zvonareva breaking immediately to jump out to an early lead and despite struggling on her own serve she wrapped it up 7-4.

Belgian Clijsters also got her campaign in Doha off to a successful start with a 6-2, 6-3 win over Jelena Jankovic in another White Group clash.

Taking the first set in 25 minutes, the Belgian stuttered on serve but treated the crowd to a shot-making masterclass.

At 2-2 in the second, Jankovic let a 40-15 lead slip with a catalogue of unforced errors and looked imploringly at her mother Snezana sitting courtside for answers.