Golden double for Bolt

The 21-year-old, who eased up before setting a record of 9.69 in the 100m on Saturday, allowed himself no such indulgence in the longer race and dipped over the line to take two hundredths of a second off Michael Johnson's 1996 mark.

"It's great, I have a great feeling, it is a dream come true," Bolt said. "I never expected this. I knew the track was a fast track but I didn't think this was possible. I'm still shocked.

"I have been aspiring to the world record for so long. I have been saying all season that 200 means a lot more to me than 100. I've been dreaming of this since way back."

Defending champion Shawn Crawford of the US took the silver in 19.96 after Churandy Martina of Netherlands Antilles was disqualified for running out of his lane and American Walter Dix got the bronze in 19.98.

Crawford and Dix finished fourth and fifth in the race but earned their medals because their compatriot Wallace Spearmon was also disqualified for stepping out of his lane.

For the second time in five days, though, the Bird's Nest belonged to the super-cool Bolt who celebrates his 22nd birthday on Thursday.

He struck a series of poses as the television cameras settled on him before he took to his blocks but again he got away cleanly and was well clear of his rivals by the halfway point.

There was no showboating over the final stages, however, and he maintained his form and loping stride before sneaking a glance at the clock as crossed the line about seven metres clear of Martina.

"It's ridiculous," said former 100 metres world champion Kim Collins, who finished last. "He's doing it and making it look so simple. It's brutal. It's a brutal ass-whipping we took."

Jamaican Prime Minister Bruce Golding led the plaudits for Bolt and said he was considering declaring a national holiday in honour of his achievements.

"We're going to wait until the Games are over because we have more gold medals to win," Golding told Reuters by telephone.

"Usain Bolt is a super human being. The world has never seen anything like him."

American Carl Lewis was the last man to win both sprints at the same Games in Los Angeles in 1984 and Bolt became just the ninth athlete to achieve the feat.

The previous world record of 19.32 was set by American Johnson in the 1996 Olympic final.