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The Guardian newspaper's editor says British authorities destroyed an unspecified number of its hard drives in an apparent attempt to keep secrets leaked by former National Security Agency contractor Edward Snowden from Chinese spies.

Alan Rusbridger made the claim in an opinion piece published Monday on the Guardian's website, saying that a pair of staffers from British eavesdropping agency GCHQ monitored the process in what he called "one of the more bizarre moments in the Guardian's long history."

He said the hard drives were torn apart in the basement of the Guardian's north London office with "two GCHQ security experts overseeing the destruction ... just to make sure there was nothing in the mangled bits of metal which could possibly be of any interest to passing Chinese agents."

It was not clear exactly when the incident occurred. Rusbridger gave a vague timeline, suggesting that it happened within the past month or so. Guardian spokesman Gennady Kolker declined to comment further, and messages left with GCHQ after working hours were not immediately returned. An operator at the intelligence agency's switchboard said no one was available until Tuesday.

Rusbridger said the destruction was the culmination of weeks of pressure on the Guardian by British officials.

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    Shortly after his paper began publishing reports based on Snowden's leaks, he said he was contacted by "a very senior government official claiming to represent the views of the prime minister" who demanded the return or destruction of Snowden's material. There followed a series of increasingly tough meetings in which officials demanded the Guardian comply. Eventually, he said, officials threatened legal action, and that's when the editor allowed British agents into his basement.

    A spokesman for British Prime Minister David Cameron declined comment.

    Rusbridger said the destruction wouldn't curb the Guardian's reporting, suggesting that copies of the Snowden files were held elsewhere and that reporting would continue outside the U.K. He added that British police's recent detention of David Miranda -- the partner of Guardian reporter Glenn Greenwald -- and the seizure of the former's laptop, phones, and other devices would similarly have no effect on Greenwald's work.

    Snowden's leaks -- published in the Guardian, The Washington Post, and other publications -- have exposed the details of the United States' global surveillance apparatus, sparking an international debate over the limits of American spying. And as lawmakers debate reforms and civil liberties group go to court, journalists have been wrestling with the implications of mass surveillance.

    Rusbridger said Monday that the spies were growing so powerful "it may not be long before it will be impossible for journalists to have confidential sources."

    Meanwhile, G29, an umbrella organization that includes data protection agencies across Europe, said Monday it wrote EU Justice Commissioner Viviane Reding last week to demand details on the extent of U.S. surveillance efforts in the wake of the leaks.

    The organization said in a statement it is demanding "specifics regarding the exact nature of the data collected" by PRISM, and details on how U.S. authorities access Europeans' data and the recourse EU citizens have.

    The National Security Agency's PRISM operation compels major Internet firms to hand over detailed contents of communications such as emails, video chats and more.

    Germany's independent privacy watchdogs say the surveillance programs breach an EU-U.S. pact meant to ensure cross-border data protection.

    The Associated Press contributed to this report.