LONDON - Tamils and their supporters demonstrating outside Britain's parliament on Monday refused to believe that Sri Lanka's long civil war was over or that separatist Tamil Tiger rebels were defeated.

It's not true, no way, Sri Lankan-born Jey Moorthy, 23, said of Sri Lanka's declaration of total victory in one of the world's most intractable wars.

Police said 2,000 people took part in a noisy demonstration in central London calling for a ceasefire and help for civilians caught up in the conflict.

The protesters, some waving red Tamil flags or wearing fake bloodied bandages, sat down in a major intersection outside parliament, disrupting traffic.

They blocked a road leading to a key bridge over the River Thames, trapping buses and cars in the crowd. Scores of yellow-jacketed police officers faced the protesters, but police said the protest was peaceful and there were no arrests far.

Moorthy, who said he was proud to say I'm a Tamil Tiger, did not believe a Sri Lankan state television report that rebel leader Vellupillai Prabhakaran had been killed.

I don't think my leader (is) dead, he said. Even if he was killed another leader would emerge in his place, he said. It's going to continue. We are not going to leave it like this.

The United States, the European Union and India regard the rebel Liberation Tigers of Tamil Eelam as a terrorist group.

Samsunnisa Noorhul-Halim, 25, born in London to South Indian Tamil parents, said the war was never ever over and the Tamil Tigers were never defeated.

I do want peace, don't get me wrong, there's a lot of people that have suffered from this, but at the same time ... it's (about) human dignity, she said. There's civilians there who are trapped. There's innocent people who are being killed.

Indra Poopalapillai, 34, a Tamil, accused the Sri Lankan government of telling lies. The Tamil Tigers were not finished, he shouted emotionally, adding: They are coming back again.

While the London protesters demanded action from Britain, demonstrators in Colombo threw rocks at the British High Commission and tossed a burning effigy of Foreign Secretary David Miliband inside. Miliband is seen in Sri Lanka as sympathetic to the pro-rebel lobby.

Sri Lanka President Mahinda Rajapaksa assured British Prime Minister Gordon Brown in a phone conversation on Monday the United Nations and other international agencies would have access to people who fled the conflict, Brown's spokesman said.