Trump says FBI investigating Nvidia boss's affair with alleged Chinese spy

US President Donald Trump has said the FBI is investigating the affair between the chief executive of Nvidia and an alleged Chinese spy.

Trump said he spoke to Jensen Huang on Monday following reports that the US believed he had been targeted in a Chinese espionage campaign.

"I asked him that question, 'Did you have any idea she was a spy?' He said 'I had no idea she was a spy' and I really believe him," Trump told reporters.

Beijing has rejected claims that Huang was targeted, with its foreign ministry saying the allegations were "entirely groundless, speculative and intended to smear and malign China".