Thousands of placard-waving activists demanded an immediate Middle East ceasefire on Saturday as they rallied in London to demand a halt to the conflict between Israel and Hezbollah in Lebanon.
The demonstration passed the US embassy and Downing Street, as British Prime Minister Tony Blair worked inside on securing a United Nations resolution aimed at ending the bloody conflict.
Blair telephoned Lebanese prime minister Fuad Siniora to restate his support for his counterpart's seven-point plan for a ceasefire put forward at last week's Rome summit, Downing Street said.
London's Metropolitan Police said 15,000 people were on the protest, while the organisers, the left-wing Stop the War Coalition, claimed a turn-out around 100,000-strong.
The demonstrators massed opposite the Houses of Parliament.
Stop the War spokesman John Rees told AFP that the protest was to hammer home a message to Blair.
"It's about telling the British and US governments that we want an unconditional ceasefire. We're the people who have the power to stop the Israelis in Lebanon," he insisted.
"Their silence is permitting mass murder in Lebanon by the Israeli forces. Look at the casualties: it's eight to one."
Salma Yaqoob, chairwoman of Stop the War in Britain's second city of Birmingham, said: "We're here to protest because of Israel's attack in Lebanon and the fact that Britain, America and Israel are on one side and 160 countries are on the other side."
Among the placards were ones branding US President George W. Bush "World's number one terrorist" and others reading "Freedom for Palestine" and "Hands off Lebanon".
Demonstrators booed and chanted "George Bush, terrorist" and "murderers" as the rally passed the heavily-guarded US embassy, and some waved the green and yellow banners of the Shiite militia group Hezbollah.
Protesters stopped at the entrance to Downing Street and whistled, while others hurled children's shoes to represent the youngsters killed in the conflict.
A letter bearing 40,000 signatures was also to be handed in at Downing Street, calling on Blair to work towards ending the conflict.
Resisting international calls for an immediate ceasefire, Blair has sided with the US and insisted that any cessation of hostilities should come from both Israel and Hezbollah and be on a durable basis.
Blair's cabinet is reported to be divided on his approach to the conflict, which is proving unpopular with significant numbers of backbench MPs in his governing centre-left Labour Party.
The prime minister postponed his Caribbean holiday on Friday to stay in Downing Street and keep on the phone with other world leaders bidding to halt the conflict.
Cabinet minister John Hutton denied reports that the government was split.
The work and pensions secretary told BBC radio: "The government is very strongly behind what the prime minister is trying to do here, which is to find a way to build, yes, an immediate ceasefire that ends the death and destruction - which has got to be done - but then puts in place a process where we can allow the peace and security in the region to begin again."
Other organisers behind Saturday's protest included the British Muslim Initiative, the Campaign for Nuclear Disarmament, the Palestine Solidarity Campaign and Lebanese community associations.