Police on Tuesday arrested 57 anti-G8 protesters, some during a raid in central London ahead of a planned march and next week's summit.
Hundreds of officers surrounded a former police station on Beak Street, used by protesters as a temporary base amid the anti-capitalist Stop G8's "Carnival Against Capitalism" march in the West End, which included about 200-300 people.
London's Metropolitan Police, with a search warrant for the address, said on Twitter people in the building were "free to leave, but will be searched." After a three-hour standoff police forced their way into the building with chainsaws and crowbars.
A police spokesman said the warrant concerned intelligence that suggested "individuals at the address were in possession of weapons and were intent on causing criminal damage and engaging in violent disorder."
At least two people were arrested, one on suspicion of criminal damage, and the other on suspicion of carrying a weapon. One man who spoke to The Guardian on condition of anonymity accused the police of using unnecessary force. "I think it's police brutality, to enter a completely legal squat," he said. "They're just trying to stop any protests. It's pretty scary."
TV footage showed officers saving a protester who appeared to attempt suicide by jumping off the roof of the building.
President Barack Obama, Russian President Vladimir Putin and German Chancellor Angela Merkel, among others, will attend the G8, a forum for the world’s eight wealthiest nations.
The event, which includes surveillance drones and 3,500 UK officers for security measures, will be held at the Lough Erne golf resort in Northern Ireland from June 17-18.