Protests against the Israeli offensive in Gaza became heated last night when up to 5,000 people gathered outside the country's London embassy.
A crowd dominated by young British Muslims cheered as Israeli flags were burned and some protesters hurled missiles, including a firework, at police.
Officers sealed off roads around Kensington High Street and armed themselves with riot shields as a small number of angry protesters tried to break down barriers protecting the building.
Older members of the crowd were seen trying to calm the atmosphere, which became increasingly charged as darkness fell and news of the ground invasion began to spread.
The group had broken away from a much larger demonstration earlier in the day when thousands marched through the streets of central London and gathered at a rally in Trafalgar Square.
Police said that 12,000 people had taken part in the protest, but the Stop The War Coalition, organisers of the demonstration, said the real figure was six times that at more than 60,000.
Organisers were preparing to make an official complaint to Scotland Yard after claiming that riot police charged into protesters.
Eyewitnesses claimed a number of people, including children, were thrown to the ground during a clash in an underpass at Hyde Park at the end of the demonstration.
Chris Nineham, an official of STWC who has organised dozens of national demonstrations, said: "I have never seen policing as irresponsible as this. People were being crushed inside that tunnel and they were being batoned. It was absolute pandemonium and people were falling over from the force of the police attacks.
"There were people trying to pull their children back and prevent them from being crushed. If anyone had fallen over then it would have been a very, very different story."
Stephen Hodgkins, 38, a community worker from Battersea, said people were petrified inside the tunnel. "We tried sitting down but that didn't seem to work. It was complete panic."
The mood had been more optimistic earlier in the day when speakers addressed the crowds in Trafalgar Square.
"Look at them, it warms my heart," said Tony Benn, president of the STWC, indicating the mass of demonstrators.
Earlier, protesters had thrown more than 1,000 pairs of shoes at the heavily-policed entrance to Downing Street in a mark of solidarity with the Iraqi journalist jailed for making a similar demonstration against US President George W Bush at a press conference.
The London protest was one of 18 that took place across the UK yesterday. There were also rallies in Paris, Berlin, Rome, Athens and several Asian cities.
The protest march at the Israeli embassy in Athens turned violent as demonstrators threw stones and fire bombs at riot police, and officers retaliated with tear gas and stun grenades.
Hundreds of Israelis protested in Tel Aviv's Rabin Square, with up to 10,000, largely Israeli Arabs, taking to the streets in the northern town of Sakhnin.
In London too, the crowds kept pouring in, a mix of ages, colours, and creeds.
Even a group of Orthodox Jews had braved possible hostility and broken the Sabbath to join the protest alongside anti-war campaigners, Muslim groups and ordinary citizens.
Housing officer Derek Perry, 60, and his sculptor friend Maria Smith, 47, from West Norwood, were nursing cups of coffee in cold hands. "I just wanted to be here," said Perry. "You have to make a stand," said Smith.
A group of young men from Leicester were selling copies of Palestinian football strips. "We're nearly sold out and we brought a good 100 or more - it's all for charity," said a delighted Irshad Patel, 23, bartering furiously.
The podium around Nelson's Column had been barricaded off and speakers lined up to make an address. Peace campaigner Bianca Jagger looked down towards Parliament. "I made my speech too soon; I should have waited for them to arrive," she said.
Singer Annie Lennox was there too. Formerly married to an Israeli, she told the Observer: "This is not about political sides any more, this is a sincere and earnest yearning for peace. One and a half million people are trapped inside Gaza; what will the outcome be of a ground war? The world will never be safe again."
Others found the protest upsetting. Rabbi Dr Sidney Brichto, senior vice-president of Liberal Judaism, a federation of liberal synagogues, said: "The demonstration was easy to organise because most of the demonstrators want more than a ceasefire.
"Most of these people want the end of Israel. Hamas are able to plug into latent anti-semitism in the West. It breaks my heart."
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