Anonymous and LulzSec hacktivists 'attacked' by GCHQ

British spy agency GCHQ has been involved in carrying out cyber-attacks on the hactivist groups of Anonymous and LulzSec, according to documents obtained by NBC News.

Citing leaked documents from the former National Security Agency (NSA) contract worker and whistle-blower Edward Snowden, NBC reports that British spies shut down communications between Anonymous members using a "distributed denial of service" (DDoS) attack.

Related: NSA denies site was hacked as Anonymous members claim credit

The method is similar to that used by hackers to breach the security of retail and government websites, however it is the first known occasion of it being used by a government.

The agency targeted secure online chat rooms used by the hacktivists but may also have affected websites that had no affiliation to the groups.

Michael Leiter, the former head of the U.S. government's National Counterterrorism Centre and now an analyst with NBC News, said that governments were looking for ways to respond to attacks on their websites

"While there must of course be limitations, law enforcement and intelligence officials must be able to pursue individuals who are going far beyond speech and into the realm of breaking the law: defacing and stealing private property that happens to be online," he said.

Related: The year the NSA hacked the world – a 2013 PRISM timeline

"No one should be targeted for speech or thoughts, but there is no reason law enforcement officials should unilaterally declare law breakers safe in the online environment,"

Critics have claimed that the attacks were a breach of people's right to freedom of speech, as they targeted people for expressing their political beliefs.