Christopher Wray said he was "blown away" by the scale of Chinese efforts to steal US technology when he became FBI director in 2017.

In an exclusive interview with Sky News' US partner NBC News, the FBI director said the bureau is opening a new Chinese-related counterintelligence investigation on average every 12 hours, with more than 2,000 such cases currently under way.

Speaking about the scale of the spying activity, he said: "This one blew me away. And I'm not the kind of guy that uses words like 'blown away' easily.

"There is no country that presents a broader, more severe threat to our innovation, our ideas and our economic security than China does."

The FBI said other countries sometimes steal technology by planting spies inside a company.

But other cases involve theft committed remotely through computer intrusions.

Mr Wray said China has no equal when it comes to the second method.

"The scale of their hacking programme, and the amount of personal and corporate data that their hackers have stolen, is greater than every other country combined," he said in the interview.

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Mr Wray had earlier warned that China's economic espionage has reached a new level which is "more brazen, more damaging than ever before".

The Chinese government has repeatedly insisted that it doesn't steal US business secrets.

However, the FBI has accused Chinese spies of targeting a wide range of US innovations - including COVID vaccines, computer chips, nuclear power plants, wind turbines and smartphones.

Chinese intelligence officer Xu Yanjun was convicted of trying to steal closely guarded technology in November 2021.

It had been developed by GE Aviation for making jet engine fan blades from composite materials.

Investigators said he helped hackers get access to company computers and tried to persuade a GE engineer to travel to China.

GE Aviation alerted the FBI, and the engineer was given altered documents to let the scheme play out so investigators could build a criminal case.

Mr Wray has also long accused China of using pressure tactics to block criticism from dissidents and members of the immigrant community in the US, which he said amounts to Chinese officials exporting their oppressive tactics.