The FBI has assessed that a leak from a laboratory in the central Chinese city of Wuhan likely caused the Covid-19 pandemic, director Christopher Wray said on Tuesday, a claim China said had "no credibility whatsoever".

"The FBI has for quite some time now assessed that the origins of the pandemic are most likely a potential lab incident in Wuhan," Wray told Fox News.

His comments follow a Wall Street Journal report on Sunday that the US Energy Department had assessed with low confidence the pandemic resulted from an unintended lab leak in China.

Four other agencies, along with a national intelligence panel, still judge that the pandemic was likely the result of natural transmission, and two are undecided, the Journal reported.

White House national security spokesperson John Kirby said on Monday the US government had not reached a definitive conclusion and consensus on the pandemic's origins.

China denounced Wray's comments on Wednesday, saying it was firmly opposed to any form of "political manipulation" of the facts.

"Based on the poor track record of fraud and deception of the US intelligence community, the conclusions they draw have no credibility whatsoever," Chinese Foreign Ministry spokesperson Mao Ning told reporters in Beijing.

"...We urge the US side to respect science and facts."

Wray said he couldn't share many details of the agency’s assessment because they were classified.

He accused the Chinese government of "doing its best to try to thwart and obfuscate" efforts by the United States and others to learn more about the pandemic's origins.

The virus was first identified in Wuhan in December 2019 before spreading around the world and killing nearly seven million people.

- Reuters