Thousands of anti-capitalists, anarchists, and environmental campaigners descended for protests in several locations in London, including its financial center around the Bank of England, Britain's central bank.
Protesters broke several dark tinted windows of a Royal Bank of Scotland building and crawled inside. They also spray-painted the word "thieves" and the anarchist symbol on the side of the building.
The ailing bank has been the target of much anger following reports that its former chief executive was given a multi-million dollar pension payout despite overseeing record losses.
As evening approached, police pushed protesters towards the Bank of England to keep them penned in.
Small fires were set in the crowd of about 4,000 and effigies of bankers burned. A CNN correspondent reported many of them were frustrated at not being allowed to leave the area.
"Police are now working towards a controlled dispersal, where groups of people will be allowed to leave," the police said in a written statement just before 7 p.m. (2 p.m. EDT.)
"On the whole, it's not been too bad," a police spokesman said when pressed about the nature of the protests.
Eleven people were arrested for being in possession of police uniforms, a police spokesman told CNN. They had earlier been stopped while riding in an armored personnel carrier near Bishopsgate, close to the Bank of England. At least 32 people were arrested, including three at the RBS protest, police said.
Demonstration organizer Marina Pepper told CNN that she was disappointed with the policing. "They definitely came looking to cause trouble," she said.
Banners at the protest read "Arrest the War Criminals," "One Currency, One Country, One World," and "Capitalism Isn't Working." One protester stood in the crowd and strummed a guitar.
