The London team overhauled long-time favourites Paris as well as Madrid, Moscow and New York to win the race to stage the lucrative sports extravaganza.

International Olympic Committee President Jacques Rogge announced the winner at a globally televised ceremony after a day of presentations and deliberations at the IOC session in Singapore's Raffles City complex.

The news was greeted by screams of joy from the London team.

The 2008 Olympics will be held in Beijing

Paris and London were left in the final round of voting.

The fact that four rounds of voting were held indicated a close fight. Paris started the session as marginal favourites with London considered their closest challengers.

Under the IOC voting system, a winner is not declared until one candidate city wins a majority of votes. If not, the lowest ranked candidate in each round is eliminated.

Moscow were eliminated in the first round of voting, New York in the second and Madrid in the third. No voting figures were given.

Earlier the five cities all had their hour in the spotlight before the IOC session.

Paris and London both sent their political heavyweights to Singapore to help turn the vote in their favour.

French President Jacques Chirac took part in the French presentation in person to make an impassioned plea to the IOC. "The heart of Paris and the heart of France are beating in unison in the hope of becoming Olympic ground in 2012.

"Dear friends ... I shall vouch for this. You can put your trust in France, you can trust the French, you can trust us," he said.

Chirac flew off immediately afterwards to join the G8 summit in Gleneagles, Scotland, hosted by Prime Minister Tony Blair who spent two days in Singapore promoting the London bid.

Blair left for home late on Tuesday after attending the formal opening of the IOC session. He and Chirac, at odds over both political and rival candidature issues in recent times, were seen shaking hands amicably at the post-opening party.

Blair made his pitch in a video clip.

"Our vision is to see millions of young people participate in sport and improve their lives," he said. "London has the power to make this happen."