Stock exchange occupation blocked
Anti-capitalist protests that started with the Occupy Wall Street movement on Saturday spread to London and other cities.
Thousands of people descended on the area around the London Stock Exchange in a bid to replicate the huge demonstrations which have been taking place in New York.
A spokesman for the protesters said: "We are doing this to challenge the bankers and the financial institutions which recklessly gambled our economy. This occupation and 20 other occupations all around the UK have been directly inspired by what's happening all across America and especially Wall Street."
Activists had planned to take over Paternoster Square, where the Stock Exchange is located, but police cordoned off the area. Instead, protesters returned to their previous position in front of St Paul's Cathedral.
As night fell, they announced their intention to set up a campsite in St Paul's Churchyard, putting up tents and portaloos on one side of the square. However, Scotland Yard made it clear police would not allow the campsite in front of the cathedral, saying such a move would be "illegal and disrespectful".
The force said they had made efforts to ensure the protest was largely peaceful. Three arrests were made - two for assault on police and one for a public order offence.
Well-known activists including Julian Assange and Peter Tatchell were among the protesters. Mr Assange, creator of the Wikileaks website, addressed the crowds on the steps of St Paul's Cathedral.
Protests also took place on the streets of Edinburgh and Dublin, which passed off peacefully. More than 100 demonstrators turned out to protest in St Andrew Square, Edinburgh, while hundreds also took to the streets of Dublin.
Anna Jones, a supporter of Occupy London Stock Exchange said: "So far, we have already seen a disproportionate amount of force by the police against protesters who are occupying the area outside St Paul's... The only crime that the police can pin on people is one of having a conversation about real democracy and the unfair and unequal economic system that favours the rich and powerful."
In Italy, however, police fired tear gas and water cannons as protesters turned the demonstration against corporate greed into a riot, smashing shop and bank windows, torching cars and hurling bottles.