Italian team leader Paolo Bettini struck gold in the men's Olympic road race on Saturday while Portugal's Sergio Paulinho, ranked 279th in the world, gave his country a landmark silver medal.

Belgium's Axel Merckx, son of five-times Tour de France winner Eddy, took bronze but defending Olympic champion Jan Ullrich of Germany could finish only in the chasing pack.

World champion Igor Astarloa of Spain fell on the opening lap of the 17-lap 224.4 km course, which wound through central Athens and took the riders under the shadow of the Acropolis.

German Andreas Kloeden, a bronze medallist in Sydney four years ago and second in this year's Tour, failed to finish, as did Russian champion Viatcheslav Ekimov, who will defend his Olympic time trial title next week.

Bettini's gold comes a year after he won the World Cup overall rankings a second consecutive time and is just reward for the likeable 30-year-old, knicknamed "The Cricket".

After spending most of the race in the peleton, protected by his strong Italian team, he broke with 30 km to go and was followed only by Paulinho.

They opened a 40-second gap by the final lap of the 13.2 km course and while Merckx made a late effort to reel them in, the Italian took gold with room to spare.

Paulinho's silver is Portugal's first medal in the history of Olympic road racing.

Ullrich's failure to win means that none of the 16 winners of this race over the past 108 years have managed to defend their title successfully.