Fossil fuel revenues form the backbone of Russia's economy, which has been buffeted by sanctions following Vladimir Putin's full-scale invasion of Ukraine.

“The U.K. and its EU allies are turning the screw on the Kremlin’s war chest by stemming the most valuable funding stream of its illegal war in Ukraine even further,” British Chancellor of the Exchequer Rachel Reeves said on Friday.

The British government sanctioned three Russian intelligence units after an uptick of cyber and arson attacks.