Beijing - Usain Bolt of Jamaica redefined the men's sprint at the Beijing Olympics when he became the first man in the Games' 112-year history to get a sprint double with world records in the 100 metres and 200 metres.

Finally running hard all the way, Bolt clocked a jaw-dropping 19.30 seconds for 200m gold on Wednesday - shaving two hundredth of a second of Michael Johnson's 19.32 seconds from August 1, 1996 at the Atlanta Olympics.

The Jamaican star won the 100m gold on Saturday with a stunning world record of 9.69 seconds.

Bolt is the first man since Carl Lewis 1984 in Los Angeles and the ninth overall to win the 100m and 200m at one Olympics. He is also only the second Jamaican to win the 200m gold, following Don Quarrie's success in 1976.

Churandy Martina got silver for the Dutch Antilles in 19.82 seconds and the 2004 gold medallist Shawn Crawford got bronze in 19.96 after fellow-American Wallace Spearmon (19.94) was disqualified.

There was more joy for Jamaica when Melanie Walker won 400m hurdles gold and Aksana Miankova won hammer throw gold for Belarus in the day's only other two medal events.

Bolts run proved Johnson wrong, who had just hours earlier predicted that his record would not fall on the night.

"I don't think he'll break it here. I will be shocked if he does. To run 19.3 he's going to have to run the curve a lot better and hold his speed to the line. But then I didn't think he was going to run 9.69," said the American legend who also owns the 400m world record.

Johnson also named Bolt's 100m win "the most impressive athletic performance I've ever seen in my life."

Bolt led from the start and stormed away from everyone on the home straight in an awesome display of strength. This time he didn't ease up and crossed the line in 19.31, the official time then named at 19.30 in a new athletics milestone.

Johnson's mark was considered almost untouchable until the arrival of Bolt. American Tyson Gay had the second best all-time result three tenth behind Jackson on 19.62. Bolt's personal best until Wednesday was 19.67 seconds.

Walker the hurdles in the fourth best time ever of 52.64 seconds. Sheena Tosta of the US got silver in 53.70 and Tasha Danvers secured bronze for Britain in 53.84 seconds.

The season-leader Miankova got the winning hammer throw of 76.34 metres in her fifth attempt.

Two-time world champion Yipsi Moreno of Cuba had to settle for silver as in 2004 with 74.40m. Zhang Wenxiu threw 74.32m in front of a happy home crowd to add Olympic bronze to the one she won at the 2007 worlds.

In preliminary action, Olympic champion Yuriy Borzakovskiy of Russia qualified handily for the 800m semi-finals along with Sudan's teenage sensation Abubaker Kaki and experienced Kenyan Wilfried Bungei, who led the way with 1:44.90 minutes.

The 10,000m gold medallist Kenenisa Bekele of Ethiopia and world champion Bernard Lagat of the US advanced into the 5,000m final while Tuesday's 1,500m champion Rashid Ramzi of Bahrain withdrew before the start.

World record holder Dayron Robles dominated the 110m hurdles semi-finals in 13.12 seconds while three Americans and three Jamaicans will be among the women's 200m finalists, with Jamaican Veronica Campbell-Brown fastest in the semis on 22.19 seconds.

It was revealed earlier Wednesday that heptathlon silver medallist Lyudmila Blonska of Ukraine tested positive for a steroid. She faces being stripped of the medal and a lifetime ban, having already served a two-year suspension 2003-2005 for steroid abuse.

Blonska finished second at the Olympic heptathlon on Friday and Saturday behind compatriot Natalya Dobrynska. American champion Hyleas Fountain was third in the heptathlon and Tatiana Chernova of Russia fourth as both could be bumped up to silver and bronze, respectively.

A ruling by the International Olympic Committee was expected on Thursday.

Thursday medal events are the women's 200m, 20km walk and javelin as well as the men's 400m, 110m hurdles and triple jump. The decathlon will also start.