Nvidia and its chief executive, Jensen Huang, have been accused of defrauding shareholders in a lawsuit over the Chinese spying scandal engulfing the $4.3tn (£3.2tn) company.

The legal action came as Donald Trump said the FBI was investigating Huang's affair with an alleged Chinese spy.

According to a complaint filed in federal court in San Jose, ​California, the Nvidia and Huang misled shareholders in connection with the executive's alleged ​affair with Alice Huang, a former executive of Singapore-based ⁠Megaspeed who is not related to him.

The shareholders claim both parties did ​not disclose that the matter raised national security concerns that it ​threatened Nvidia's reputation and business prospects.

The New York Times reported on the alleged relationship last month, and said US authorities had concluded Alice Huang ​was a Chinese intelligence asset.

Nvidia did not immediately respond to ​a request for comment to Reuters.

Jensen Huang told Nvidia's employees he had been unfaithful to ‌his ⁠wife, without disclosing details of the alleged relationship.

He co-founded Nvidia in 1993 and has led the California company as it became the world's most valuable chipmaker and made him ​one of the ​world's most ⁠prominent symbols of the artificial intelligence boom.

Nvidia announced on Sunday it was conducting an independent investigation into reports that Huang was the "target of a foreign intelligence effort". Shares in the company tumbled on Monday, closing down 4.3%, reducing Nvidia's ​market ⁠value by approximately $190bn. The lawsuit was filed five minutes after the US stock market closed.

It is common for shareholders to ⁠sue ​companies after unexpected share price declines. ​Nvidia shareholders, led by Mark Kistenmacher, a retail investor, are seeking unspecified damages from the defendants.

Trump said on Monday that the FBI is investigating Huang's affair but said he does not think the executive has a reason to worry.

"I know the FBI is looking into it in terms of something else, and I think that he'll be in good shape," Trump said at a White House briefing.

"I did speak to him today just to see if he's feeling all right, how you're doing," Trump said. "He said he had absolutely no idea that the person in question was a spy."

Huang said in an open letter posted on Nvidia's website: "I support the investigation and will cooperate fully. I love our country and our company. I am committed to protecting Nvidia and supporting America's national security,"