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Hundreds of activists have clashed with police, causing damage to buildings and bringing disruption to central London.
Protesters, unconnected to the anti-government cuts rally, were in a stand-off with officers in Piccadilly. A group of 200-300 were later contained by police in Trafalgar Square.
Demonstrators had earlier smashed windows and set off fireworks outside shops and banks in Oxford Street.
Union leaders said the violence must not overshadow the peaceful main march.
More than 250,000 people took part in a Trades Union Congress-organised march from Victoria Embankment to Hyde Park.
But a group of about 500 people gathered in Oxford Street, before targeting the Topshop fashion chain's flagship store and the banks Santander, HSBC and RBS.
The Metropolitan Police said 214 people were arrested for a variety of offences, including public order offences, criminal damage, aggravated trespass and violent disorder.
There were 66 reported injuries over the course of the day, including 13 police officers. Sixteen were taken to hospital, including one officer.
Police said officers later came "under sustained attack as they deal with the disorder and attempted criminal damage" in Trafalgar Square.
A Met Police spokesman said missiles had been thrown and attempts were made to damage the Olympic clock.
But after a few hours of containment by police, during which people in the square were only allowed to leave in small groups via its north-eastern corner, there was just a small number of protesters remaining.
BBC engineer Chris Doherty, who was at the square shortly at 2330 GMT, estimated that the containment zone contained fewer than 50 people.
Police were attacked as they tried to stop them smashing their way into banks and shops. They said they came under attack from protesters throwing lightbulbs filled with ammonia.
Officers followed the black-clad mob as they surged along Piccadilly, Regent Street and Oxford Street, the UK's busiest shopping district. The world famous Ritz hotel in Piccadilly suffered damage, as did a Porsche showroom.
The BBC's Tim Willcox said the situation was beginning to return to normal in Oxford Street and Piccadilly at about 2000 GMT.
Scotland Yard commander Bob Broadhurst said he had anticipated there would be some problems.
"They are engaging in criminal activities for their own ends," he said.
"We'll never have enough officers to protect every building in central London."
In a separate incident, about 200 supporters of campaign group UK Uncut staged a sit-in at luxury Piccadilly store Fortnum & Mason.
A spokesman for the demonstrators said the store was chosen because part-owners Whittington Investments "dodge tens of millions in tax".
TUC General Secretary Brendan Barber said he "bitterly regretted" the violence, adding that he hoped it would not detract from the massive anti-cuts march.
"I don't think the activities of a few hundred people should take the focus away from the hundreds of thousands of people who have sent a powerful message to the government today," he said.
Labour leader Ed Miliband, who spoke at the rally, said there was "no excuse" for the violent scenes.
"I unequivocally condemn those who have committed acts of violence," he added.
Policing minister Nick Herbert said "a small minority of individuals were intent on disorder".