Britain has been forced to remove some of its spies after Russia accessed the top-secret documents taken by former US intelligence contractor Edward Snowden, British media reported.

The BBC and the Sunday Times cited senior government and intelligence officials as saying agents had been pulled, with the newspaper saying the move came after Russia was able to decrypt more than one million files.

Additionally, the government has been prevented from getting vital information, a Downing Street source said, according to the newspaper.