Demonstrators clashed with riot police and smashed the windows of a bank in London's financial center on Wednesday in protest against a system they said had robbed the poor to benefit the rich.
Hundreds of protesters converged on a branch of the Royal Bank of Scotland, shattering windows.
Rescued by the government in October, RBS has become a lightning rod for public anger in Britain over banker excess blamed for the crisis. The protests were timed to coincide with a G20 meeting of the world's leading and emerging economies.
Mounted police and officers in riot gear surrounded the building to keep the crowds back. Protesters hurled paint bombs and bottles, chanting: These streets, our streets! These banks, our banks!
Police said a number of officers had been injured, and minor scuffles broke out as the afternoon progressed.
Generally, though, the situation appeared to be dying down and commuters in the small area of London affected by the clashes began to leave work for home.
HORSEMEN OF THE APOCALYPSE
Earlier, protesters marched behind models of the four horsemen of the apocalypse representing financial crimes, war, climate change and homelessness.
Some threw eggs at police and chanted build a bonfire, put the bankers on the top. Others shouted jump and shame on you at financial sector workers watching the march from office block windows.
I am angry at the hubris of the government, the hubris of the bankers, said Jean Noble, a 60-year-old from Blackburn in northern England.
I am here on behalf of the poor, those who are not going to now get their pension or who have lost their houses while these fat cats keep their bonuses, hide their money in tax havens and go and live where nobody can touch them.
A smaller demonstration against Britain's military role in Iraq and Afghanistan attracted several hundred people in Trafalgar Square, not far from parliament.
Police said they had deployed one of Britain's biggest security operations to protect businesses, the Bank of England, the London Stock Exchange and other financial institutions.
The protests, which brought together anti-capitalists, environmentalists, anti-war campaigners and others, were meant to mark what demonstrators called Financial Fools' Day -- a reference to April fool's day which falls on April 1.
Some 4,000 protesters thronged outside the central bank, and a Gucci store nearby was closed and its windows emptied.
RBS said in a statement it was aware of the violence outside its branch and had already taken the precautionary step of closing central branches.
Wooden boards covered the war memorial in front of the Royal Exchange, once the center of commerce in the City of London and now an upmarket shopping center. Building sites and roadworks in the financial district were sealed to stop people using building materials as weapons, police said.
Police stopped a military-style armored vehicle with the word RIOT printed on the front and a police spokesman said its 11 occupants were arrested for having fake police uniforms. By mid-afternoon a total of 19 people had been arrested.