Russia's Kaniskina wins 20km walk

Russia's Olga Kaniskina led from the start and battled through relentless rain to win Olympic gold in the women's 20-kilometre walk on Thursday.

World champion Kaniskina jumped to the lead on her first step and slowly pulled away from the pack as she built a decisive one-minute lead going into the final kilometres to finish in an Olympic record of one hour, 26 minutes and 31 seconds.

"I haven't broken the world record because of the weather (but) it was better than a sunny and hot day," Kaniskina said.

Athens bronze medallist Jane Saville was the leading Australian, finishing 20th in 1:31:17.

Fellow Australian Claire Woods was 28th and Kellie Wapshott finished 40th, both on their Olympic debuts.

Kaniskina's victory gave Russia their fifth athletics gold, placing the Russians atop the track and field medal table ahead of Jamaica, with four gold medals.

Norway's Kjersti Platzer, silver medallist in 2000, finished second with a 36-second deficit, while Italy's Elisa Rigaudo took bronze after a late surge brought her back into medal contention.

"Today I thought I'll take the chance and if I blow it at the end, I don't care," Platzer said. "I started my Olympic career with silver and I'm ending my Olympic career with a silver."

China's Liu Hong, who finished a distant 19th at last year's world championship, came home in fourth place in a personal best time but her kick was not enough for a medal.

"I've been working so hard for the Olympic Games and that was the best I could do but I'm a little disappointed," Liu said.

European champion Ryta Turava of Belarus led the chasing pack until the final kilometres but, struggling with exhaustion, she dropped back after being forced to stop several times and finished in a distant 11th place.

Kaniskina's golden hopes got a boost halfway through the race when Tatyana Kalmykova, Russia's national champion and one of the main challengers, was disqualified for not making contact with the ground.

China's Yang Mingxia, who was also seen as a potential medal contender, was also disqualified