Both players were badly distracted by celebrations marking Australia Day, a national public holiday, including a thunderous 21-gun salute nearby as Zvonareva was broken in the second set.

Clijsters was later put off by a formation fly-past by military jets which screamed low over Melbourne's Rod Laver Arena as she played Radwanska.

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"No one told me there would be the noise (from the cannons). I was trying to keep my concentration but I was a bit distracted," Zvonareva said.

A medical drama involving a female fan also disturbed the Russian, but she recovered from losing her serve set to quickly close it out against the tiring Kvitova.

Zvonareva also wore a black ribbon on her cap to support victims of Monday's deadly suicide bombing at Domodedovo airport in Moscow, her home city, which killed 35 and left her frantically calling relatives.

"You're calling back home and making sure everyone is okay, the people that you know," she said. "I just tried to put it away. It happened, it is terrible. But you try to move on."

The 26-year-old remains on course for her third straight Grand Slam final, after losing to Serena Williams at Wimbledon and Clijsters at the US Open in September.

The Russian was playing her third Czech left-hander in a row after Lucie Safarova and Iveta Benesova, and she was clearly comfortable against Kvitova, whose nine-match unbeaten run came grinding to a halt.

"I don't think I was nervous," said Kvitova, 20, who won this month's Brisbane International. "But I was little tired. It's 10 matches in a row so it was tough."

Clijsters overcame a high mistake rate to see off Poland's Radwanska, who played a limited game but stayed in the match with some scrambling defence, taking advantage of the Belgian's 37 unforced errors.

"I didn't feel that great," said the Belgian. "I felt heavy in the legs -- I felt tired out there but I just hung in there."

World number one Caroline Wozniacki will face China's Li Na in Thursday's other semi-final, with both women seeking their first Grand Slam wins.

Britain's Andy Murray was playing Ukrainian Alexandr Dolgopolov in the men's quarter-finals, while top seed Rafael Nadal was due to face Spanish compatriot David Ferrer later.

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