Just Stop Oil activists sprayed orange paint on the London MI5 building and fire extinguishers outside the Home Office.
Climate protesters also covered News UK headquarters and the Bank of England in paint in a spate of action in central London 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.
Just Stop Oil has promised to protest every day this month to demand an end to all new oil and gas licenses.
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Scotland Yard said protesters threw paint at several locations on Monday morning, naming Marsham Street, Millbank, London Bridge and Threadneedle Street.
“The agents responded quickly to all incidents and a number of people have now been arrested on charges of criminal harm,” the force tweeted.
City of London police confirmed that two people were arrested outside the Bank of England.
Videos shared by Just Stop Oil showed bright orange paint sprayed on the glass entrance to News UK’s London Bridge building, which houses The times, the sun and Talk Radio among other media.
They also show an activist being taken away by someone in a high-visibility jacket after spraying paint on the Home Office.
Another video shows a protester spraying orange paint on the Bank of England, while another writes “Just Stop Oil” on the neighboring building.
A spokesperson for the group said Monday: “We are not prepared to stand by and watch as everything we love is destroyed, as vulnerable people go hungry and fossil fuel companies and the rich profit from our misery.
“The fossil fuel era should be long over, but the creeping tentacles of fossil fuel interests continue to corrupt our politics, government and media, as they have for decades.”
They added, “Well, we’re done begging. We are taking action to stop the new oil and gas because it is the right thing to do ”.
Just Stop Oil sprayed orange paint on other buildings in central London this month as part of its protests, including luxury car showrooms and an influential fossil fuel lobby headquarters.
Last week, activists were arrested after throwing a chocolate cake in the face of a waxwork of King Charles III at Madame Tussauds.
Its protesters are also blocking the streets around the capital, with some sticking to the asphalt. Earlier this month, two climbed a bridge over the Thames to block the key passage across the river.
Further reporting by the PA