Edward Snowden, former NSA contractor

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.

Downing Street said on Sunday that it doesn't "comment on intelligence matters" while the Foreign Office said: "We can neither confirm or deny these reports".

The BBC reported, meanwhile, that a government source said there was "no evidence" any spies were harmed.

Snowden fled to Russia after leaking the documents to the press in 2013 in a move he said was needed to expose the extent of US online surveillance programs and to protect "privacy and basic liberties".

The Sunday Times said other government sources claim the revealed US and British intelligence techniques have led to fears that their spies could be identified.

Snowden worked as a contractor at the CIA and National Security Agency, where he was able to download 1.7 million secret documents that showed how hundreds of millions of people had been under surveillance by the authorities.

He previously claimed that "no intelligence service" could crack the documents, saying he was able to "keep such information from being compromised even in the highest threat counterintelligence environments".

But an intelligence source told the Sunday Times that they know Russia has access to Snowden's material and will be going through it for years to come, searching for clues to identify potential targets.

An official from the Interior Ministry added that Russian President Vladimir Putin "didn't give him asylum for nothing".

The US administration has branded Snowden a hacker and a traitor who endangered lives by revealing the extent of the NSA spying program.

But he has been nominated for the Nobel Peace Prize for the second year in a row and has received a string of international awards for free speech and civil liberties.

AFP - Reuters