The three fastest men ever cruised through their opening 100 metres heats under clear blue skies at the start of the Olympic athletics programme on Friday.

World record-holder Usain Bolt [Images], Jamaican compatriot Asafa Powell [Images] and world champion Tyson Gay [Images] looked in fine form in the first of four rounds culminating in Saturday evening's final.

There were no major upsets in qualifying for the men's shot and hammer, while American Hyleas Fountain was the early pacesetter in the heptathlon.

Bolt, who holds the world record of 9.72 seconds, went in the first heat in front of a near-91,000 National Stadium full house.

He eased out of the blocks, picked up his running just enough to get his long stride working and coasted from halfway to cross the line in 10.20 seconds, a time that would have won gold in the final of the 1980 Games.

Powell put more into his race and was clear after 20 metres. He too eased off but still clocked a lively 10.16.

The former world record holder said he had suffered with stomach problems after his breakfast but was happy enough.

All eyes were on Gay when he came out of the blocks in his first competitive outing since pulling a hamstring in the U.S. trials last month but he looked comfortable in posting 10.22.

"It feels good," he said." "I felt a little sluggish but my body has woken up now."

Tyrone Edgar, virtually ignored at the British trials in the furore over whether banned Dwain Chambers would be allowed to go to the Games, was the fastest qualifier in 10.13 seconds.

The second round takes place on Friday night, when the first two medals, in the men's shot and women's 10,000, are also up for grabs.

All the big names advanced safely into the shot final. Pole Tomasz Majewski led the way with a personal best of 21.04 metres while Andrei Mikhnevich of Belarus, and U.S. trio Adam Nelson, Reese Hoffa and Christian Cantwell, seeking the first clean sweep in the event since 1960, also qualified easily.

Nelson, silver medallist in the last two Olympics [Images], pulled an intercostal muscle in his ribcage on Monday and said: "Every time I breathe it hurts but it's a case of mind over matter."

Defending hammer champion Koji Murofushi of Japan [Images] and world leader Ivan Tsikhan of Belarus qualified for Saturday's final with first throws, while Hungary's Krisztian Pars was the best qualifier and the only man to break the 80-metre mark.

With all-conquering Swede Carolina Kluft opting not to defend her title the heptathlon is up for grabs. Fountain made a terrific start with a 12.78 seconds 100 metres hurdles followed by a confident personal best of 1.89 metres in the high jump.

Pamela Jelimo, the 18-year-old Kenyan who has dominated the 800 metres this season, showed no signs of freezing on the biggest stage as she advanced to the semi-finals.

At the other end of the age spectrum, 35-year-old Maria Mutola of Mozambique, winner in 2000, was the fastest qualifier.