FBI director James Comey has accused China of engaging in widespread corporate hacking in an attempt to steal trade secrets from America's biggest companies.
Speaking on CBS, Mr Comey said Chinese hackers have repeatedly and deliberately targeted US firms in cyber-attacks that have cost American companies billions of dollars.
"There are two kinds of big companies in the United States," he added. "There are those who've been hacked by the Chinese, and those who don't know they've been hacked by the Chinese."
His comments come just days after JPMorgan, America's biggest bank by assets, revealed customer information-including names, addresses and e-mails- belonging to more than 70 million clients had been compromised following a hack attack in summer.
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In recent months, American authorities have stepped up the rhetoric against cybercrime, responding to concerns from companies from Wall Street to Silicon Valley, which have repeatedly complained about hacking.
Earlier this year, the US Justice Department levelled criminal charges against five Chinese military officials, accused of masterminding government-led cyber attacks to steal trade secrets from six major American companies in the key energy and metals industries.
At the time, Chinese officials denied the allegations, insisting that "the Chinese government, the Chinese military and their relevant personnel have never engaged or participated in cybertheft of trade secrets."
Mr Comey went on to say there other nations that are currently engaging in cybercrimes against the US, but did not name them. However, when asked about suggestions that "a lot of cybercrime comes out Russia", he added: "No doubt about that".