Just Stop Oil said its supporters sprayed paint from fire extinguishers on the Home Office, the MI5 building, the Bank of England and the headquarters of News Corp at London Bridge on Monday morning.
The group said the buildings were chosen to represent the pillars that support and maintain the power of the fossil fuel economy.
Scotland Yard said protesters threw paint in a number of locations, naming Marsham Street, Millbank, London Bridge and Threadneedle Street.
“Officers responded quickly to all incidents and a number of people have now been arrested on suspicion of criminal damage,” the force tweeted.
City of London Police said two people were arrested outside the Bank of England.
A Just Stop Oil spokesperson said: “We are not prepared to stand by and watch while everything we love is destroyed, while vulnerable people go hungry and fossil fuel companies and the rich profit from our misery.
“The era of fossil fuels should be long gone, but the creeping tentacles of fossil fuel interests continue to corrupt our politics, government and the media, as they have for decades.
“How else do you explain a Government ignoring sensible no-brainer policies like renewables, insulation and public transport, which would cut our energy bills and our carbon emissions, in favour of corrupt schemes to drill for uneconomic oil and gas at taxpayers expense?
“Well we’re done with begging. We are acting to stop new oil and gas because it is the right thing to do.”