Jamaica's Usain Bolt won 100 metres gold at the Beijing Olympics in a world record time on Saturday, running 9.68 seconds to claim victory in an exhilarating showdown with his compatriot Asafa Powell.

The 21-year-old won his country's first Olympic title in the blue riband event and capped an astonishing rise to the top of his sport.

Richard Thompson of Trinidad and Tobago won the silver and American Walter Dix the bronze.

Asafa Powell, whose world mark Bolt bettered with a run of 9.72 in May, once again failed to deliver on the big stage.

Bolt, a 200 metres specialist who had run only one professional race in the shorter distance before this year, will now turn his attention to becoming the first man since Carl Lewis in 1984 to win the Olympic sprint double.

World champion Tyson Gay missed the final after finishing fifth in his semi-final in a time of 10.05.

"I am pretty upset,'' said Gay.

"My family is here, they will be praying for me.''