Greece's Olympic sprint champion Costas Kenteris and silver medallist Katerina Thanou are on the verge of being excluded from the Olympics after the pair missed a drugs test, bringing shame on the host nation.

As China claimed the first two golds on the sweltering opening day of the Athens Games, Greek Olympic chiefs were meeting to decide the fate of the two sprinters and a source close to the national team told Reuters they would be withdrawn.

Kenteris was Greece's best hope of a medal on the track and had been tipped to light the Olympic flame at the grand opening -- an honour which finally went to widsurfer Nikos Kakalamanakis in a spectacular and widely praised ceremony on Friday night.

Kenteris was lying in an Athens hospital after he and training partner Thanou -- both of whom have denied repeated rumours of doping -- failed to show for a drugs test on Thursday and were later involved in a mysterious motorcycle crash.

International Olympic officials had been due to rule on the case of Sydney Games 200m winner Kenteris and Thanou, runner-up in the 100m four years ago, on Monday.

A two-year ban is the standard penalty for missing a doping test.

Thirteen gold medals were up for grabs on Saturday, the most widely anticipated in the pool, where 19-year-old American Michael Phelps is aiming for a record eight gold medals.

FIRST GOLD

The first gold of the Games went to Du Li, a Chinese student who came from behind to triumph in the women's 10 metre air rifle ahead of rivals from Russia and the Czech Republic.

"I wasn't fully prepared mentally at the start," Du, 22, said at a tumultuous news conference that was translated into four languages and interrupted by Chinese reporters asking for autographs and souvenir photos.

"But I regained my confidence from the second shot. Before my last shot I was fully confident. I wasn't nervous at all."

Wang Yifu completed the Chinese double with a similar last-shot win over two Russian competitors in the men's 10-metres air pistol event.

At the Aquatic Centre, both Phelps and Ian Thorpe of Australia -- the two biggest names in swimming -- qualified easily for the evening finals in their respective events.

"I'm just glad to finally be here," Phelps said after qualifying fastest for the men's 400 metres individual medley final, almost a second ahead of his nearest rival.

"I felt comfortable and in control today. I'm not worried about the time, I just want to get my hand on the wall first."

Thorpe, 21, was second-fastest in the 400 metres freestyle heats but remains favourite to take the title, adding to his three gold and two silver medals from Sydney four years ago.

HOT AT THE HEATS

While athletes shrugged off problems with the heat, spectators found it tougher going. At the Aquatic Centre, where organisers abandoned plans to construct a roof for the Games, temperatures rose to around 37 degrees Celsius.

"You can only last for a couple of races and then you need to go and stand outside in the shade and wait for the breeze to kick in," said spectator Leslie Lanne, watching sister Colleen help the U.S. team make the 4x100 metres freestyle relay final.

Friday night's flawless opening ceremony combining ancient mythology and high technology provided a welcome respite for Greeks depressed by the drama around their two sprinters.

"A dream which erases the nightmare of Kenteris and Thanou," Greece's Eleftherotypia daily said. "They were magical, dreamlike moments."

Germany's Bild newspaper said the ceremony was "More beautiful than ever before. Oh Olympia! That was gripping and absolutely beautiful."

"Athens alive" and "Day of Glory" were just two of the headlines from Australia, host in 2000 to one of the most successful Games in Olympic history.