Protesters from environmental group Greenpeace disabled some of BP's 50 petrol stations in central London on Tuesday in protest at the Gulf of Mexico oil spill.
Greenpeace said its activists had managed to close down 47 service stations in the capital. BP confirmed 30 had been forced to close temporarily. The company branded the demonstrations an act of vandalism and said it would reopen the sites as soon as it was safe to do so.
The protests coincided with BP's second-quarter results where the oil company reported a $17 billion loss and said it had set aside $32 billion to tackle the spill.
Greenpeace and BP said activists stopped the flow of fuel by flipping safety switches on forecourts before removing them to prevent the service stations from reopening.
BP described the action as an irresponsible and childish act which interfered with safety systems.
The action shows a total disregard for the safety of motorists and staff at the sites, a BP spokeswoman said.
She said one of the sites affected is used to supply ambulances with fuel.
At one station in Camden, north London, Greenpeace climbers replaced BP's logo with a new version showing the green sunflower disappearing into a sea of oil.
The pressure group said the protests had been planned to urge new chief executive Bob Dudley to move away from his predecessor's obsession with high risk, environmentally reckless sources of oil.
Greenpeace Executive Director John Sauven said: The moment has come for BP to move beyond oil. Under Tony Hayward the company went backwards, squeezing the last drops of oil from places like the Gulf of Mexico, the tar sands of Canada and even the fragile Arctic wilderness.
We've shut down all of BP's stations in London to give the new boss a chance to come up with a better plan. They're desperate for us to believe they're going 'beyond petroleum'. Well now's the time to prove it.
(Reporting by Stefano Ambrogi; Editing by Keith Weir and Jon Loades-Carter)