Trouble has broken out at the Million Mask March, with protesters throwing missiles and setting off fireworks and flares in central London.
A police car was set alight and its windscreen smashed near Green Park as thousands of anti-capitalist campaigners flowed past the capital's landmarks wearing the trademark Guido masks synonymous with the Anonymous hacking group.
What started off as a peaceful protest descended into violence as activists clashed with officers.
Some protesters were treated for bloody injuries and were given first aid at the scene.
There was a sudden surge of activity about half an hour into the event, as several people at the front broke off and ran towards the Churchill War Rooms.
Crowds gathered outside Buckingham Palace, a long way from the agreed route.
Some tried to enter Great George Street, a short distance from Conservative Party headquarters, which was closed off.
A line of police and mounted officers formed a barrier against the densely packed protesters, some screaming about inequality.
Stray bottles were thrust over the barriers towards officers, which was met with cheers and chants of "Shame on you, we're human too."