Waving banners under a bright blue sky, the protesters shouted: "No justice. No peace. Troops out of the Middle East," as they marched through the streets to attend the rally.

Carrying pictures of war victims and placards saying: "No occupation, No War," the crowd wound its way through central London, some chanting "Blair calls it liberation, it looks to us like occupation."

British Prime Minister Tony Blair has been US President George W. Bush's staunchest ally on Iraq, sending 45,000 soldiers, sailors and airmen into battle -- amounting to a quarter of Britain's armed forces.

With coalition forces in control of much of Iraq, Britain announced Friday that it would start to draw down its forces in the Gulf, 23 days after the start of the US-led war to oust Saddam Hussein.

Protesters laid flowers, wreaths and cards outside Downing Street before stopping again for a minute's silence in Parliament Square, opposite Big Ben and the House of Commons.

"A minute of silence for the children, the women and the men of Iraq, all the civilians victims of the war," shouted an organiser on a megaphone, as the chants and whistles died down momentarily.

"Five thousand civilians have already died in Iraq and there are many other reasons to work for the liberty of Iraq," Labour MP Jeremy Corbyn told AFP before he addressed the rally that had amassed in Hyde Park.

Police estimated the throng at 20,000 although the organisers, the Stop the War Coalition, an umbrella group for Britain's anti-war organisations, claimed there were in excess of 100,000 on the march.

"We did not march to defend dictatorship but for peace and justice," Corbyn said, adding that the US-led intervention in Iraq was "looking more and more like a colonial occupation."

British socialist film director Ken Loach went further still: "We have to stop the occupation. This is illegal. This is against international law."

"It is important we keep telling people it is not in our name. This is war for big US corporations," he said.

Some organisers of the anti-war movement had been accused of "hijacking" the strong public feeling against military action in Iraq for their own ends.

"They are hard-line Marxists whose agenda is very different to those who are doing the demonstrating," said Labour MP David Winnick.

But Kate Hudson, vice-chairwoman of the Campaign for Nuclear Disarmament (CND), said the march was a response to the fact that the war was still continuing, people were being killed and illegal weapons such as cluster bombs were still in the field.

"We also take the view that this is, of course, an illegal war. We'd like our troops to be brought home now," she said.

Saturday's march is the third held in the capital in recent weeks over the Iraqi conflict, and was planned to coincide with a massive protest in Washington.

On February 15, more than one million people took to the streets of London to protest the then looming war on Baghdad in what police said was the largest demonstration in the British capital.

On March 22, two days after the start of hostilities, between 200,000 and 700,000 people protested here.

SPACE.WIRE