Beijing - Usain Bolt, Asafa Powell and Tyson Gay were untroubled in the heats of the blue-riband 100 metres as the athletics competition of the Beijing Olympics got underway on Friday.

The world record holder Bolt (9.72 seconds) had 10.20 seconds, fellow-Jamaican former world record holder Powell (9.74) clocked 10.16 and the American world champion Gay (9.77) ran 10.22 into the second round.

Powell was seen grimacing on a physio's bench after his heat, pointing at his stomach. It was unclear what the problem was.

Gay was the only one to make a brief statement afterwards, saying: "I felt a little sluggish but my body woke up."

The second round was set for later Friday, while the semi-finals and the hyped final is on Saturday.

"This is definitely one of the hottest 100m in Olympic history," said Gay, who expects "a real fast time" required for gold.

The 2004 champion Justin Gatlin is not in Beijing because of a doping ban.

Powell and Gay are coming off injury layoff-offs in late spring, while 21-year-old Bolt has been the revelation of the season with his world record run on May 31 in New York.

Jamaica has never won Olympic 100m gold, while a victory for Gay is also important for the whole US Olympic team in its battle with host China for first place in the overall medals table.

The first two athletics finals were scheduled for Friday night, the women's 10,000 led by reigning world champion Tirunesh Dibaba, and the men's shot put.

Tomasz Majewski led shot put qualifying in the morning with 21.04m, with 2005 world champion Adam Nelson of the US also through along with compatriot 2007 worlds winner Reese Hoffa and 2004 Olympic champ Yuriy Bilonog of Ukraine.

The women's heptathlon got underway with Hyleas Fountain best over the opening 100m hurdles with 12.78 seconds for 1,158 points. British hope Kelly Sotherton has 1,097 points and world championship silver medallist Lyudmila Blonska of Ukraine on 1,078 points.

Not present was Carolina Kluft, who will only compete in long jump after winning every big heptathlon 2002-2007. Former world champion Eunice Barber is also not there and Briton Jessica Ennis is injured.

Set for later in the session was the first round of the women's 800m with Kenyan sensation Pamela Jelimo, men's hammer throw qualifying, and heptathlon's high jump portion.