JUYONGGUAN -- Spanish climber Samuel Sanchez claimed his biggest ever career win when he claimed gold in the men's grueling Olympic road race, held over 245km here on Saturday.

Italian Davide Rebellin finished a close second to take the silver medal with Switzerland's Fabian Cancellara placing third to take the bronze.

Pre-race favorite and reigning champion Paolo Bettini of Italy was left trailing after a decisive attack on the final climb by Australian Cadel Evans.

That move also dropped his fellow favorite Alejandro Valverde of Spain, and ultimately led to a six-man finish after a tough 6hr 23min 49sec of racing in 26 degrees Celsius and 90 percent humidity.

Valverde finished 22sec down in a group containing Evans, with Bettini at 35.

A thrilling end to the first big endurance test of the Games bore witness to a tough race of attrition that proved too much for some of the 143 starters, 18 of whom dropped out with two of seven laps of a hilly 23.8km loop to race.

Austrian Christian Pfannberger launched an audacious solo attack around 40km from the finish shortly after 2007 Tour de France champion Alberto Contador had dropped back following a spell of work for Valverde.

But despite his efforts he went into the final lap with just a 20sec lead. He wasn't helped by the fact he dropped his water bottle before the final, 9km climb.

He was caught early on the final climb, prompting an attack by Tour de France runner-up Evans.

The Australian's move left Bettini and Valverde behind and created a leading bunch of around 13 riders which included compatriot Mick Rogers, American Levi Leipheimer and Rebellin among others.

Another attack, this time from Luxembourg's Andy Schleck, split the leaders, forcing Rebellin, Rogers, Russian Alexander Kolobnev and Spaniard Samuel Sanchez to go off on their own.

With Evans and a few other contenders sitting just 10secs in their wake, Schleck's insistence, with another fierce turn of pace on the climb around 14km to go, whittled the group down further.

It ultimately left the 23-year-old Luxemburger with formidable Italian Rebellin and Sanchez on his wheel and proved too much for Rogers, who was left struggling to follow with Kolobnev, the Russian gasping for air.

On the long flat section leading to the uphill finish line, however, Kolobnev and Rogers did well to close the gap and soon caught sight of the leading trio with 4km to race.

Further behind, Cancellara had jumped out of Evans' group and produced a huge effort worthy of his three world time trial crowns to close the gap to Rogers.

Together, they caught the leading trio with barely a kilometer to race.

As they approached the short uphill finish, Kolobnev pulled to the front, but his effort was countered by both Sanchez and Rebellin, a formidable racer in the hilly one-day classics races in Europe.

With just 250 meters to go, Sanchez produced a turn of pace which gave him the edge. Even before the finish line - where he crossed himself after a hellish day in the saddle - the Spaniard realized he had secured a well deserved win.