Britain has pulled out agents from operations in "hostile countries" after Russia and China cracked top-secret information contained in files leaked by former US National Security Agency contractor Edward Snowden, according to the UK's Sunday Times newspaper.
Security service MI6, which operates overseas and is tasked with defending British interests, has removed agents from certain countries, the newspaper said, citing unnamed officials at the office of British Prime Minister David Cameron, the Home Office - the name used in Britain for interior ministry - and security services.
The US wants Snowden to stand trial after he leaked classified documents, fled the country, and was eventually granted asylum in Moscow in 2013.
Russia and China have both managed to crack encrypted documents which contain details of secret intelligence techniques that could allow British and US spies to be identified, the newspaper said, citing officials.
"It is the case that Russians and Chinese have information. It has meant agents have had to be moved and that knowledge of how we operate has stopped us getting vital information," a prime ministerial source said, according to the Sunday Times.
'No spy harmed'
Snowden fled to Russia after leaking the documents to the press in 2013 to expose the extent of US online surveillance programmes and to protect "privacy and basic liberties".
The Sunday Times said other government sources claimed China had also accessed the documents, which reveal US and British intelligence techniques, leading to fears that their spies could be identified.
The BBC said on its website, meanwhile, that a government source told the network that two countries "have information" that spurred intelligence agents being moved, but said there was "no evidence" any spies were harmed.
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 watched 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 counter-intelligence environments".