The top US spy agency has said for the first time that the country's intelligence community believes the COVID-19 virus that originated in China was not man-made or genetically modified.

"The Intelligence Community also concurs with the wide scientific consensus that the COVID-19 virus was not man-made or genetically modified," the Office of Director of National Intelligence (ODNI) said in a statement.

"The (Intelligence Community) will continue to rigorously examine emerging information and intelligence to determine whether the outbreak began through contact with infected animals or if it was the result of an accident at a laboratory in Wuhan," it added.

US President Donald Trump. (AP)

The ODNI statement appears to sharply contradict theories floated by anti-China activists and some supporters of US President Donald Trump suggesting that the coronavirus had been developed by Chinese scientists in a government biological weapons laboratory from which it then escaped.

Trump addressed the theory earlier this month, saying: "More and more, we're hearing the story."

Secretary of State Mike Pompeo added: "The mere fact that we don't know the answers — that China hasn't shared the answers — I think is very, very telling."

Pompeo also pressed China to let outside experts into the lab "so that we can determine precisely where this virus began."

While Trump and Pompeo have made public statements speculating about the lab, a US intelligence official disputed the notion that there was any pressure on agencies to bolster a particular theory, the Associated Press reports. The intelligence official was not authorised to publicly discuss the issue and spoke only on condition of anonymity.

Scientists say the virus arose naturally in bats. Even so, Pompeo and others have pointed fingers at an institute that is run by the Chinese Academy of Sciences. It has done groundbreaking research tracing the likely origins of the SARS virus, finding new bat viruses and discovering how they could jump to people.

"We know that there is the Wuhan Institute of Virology just a handful of miles away from where the wet market was," Pompeo said two weeks ago. The institute has an address 13km from the market that is considered a possible source.

US officials say the American Embassy in Beijing flagged concerns about potential safety issues at the lab in Wuhan in 2018, but they have yet to find any evidence the virus originated there nearly two years later.

The Chinese government said on Thursday that any claims that the coronavirus was released from a laboratory are "unfounded and purely fabricated out of nothing."

Foreign Ministry spokesman Geng Shuang cited the institute's director, Yuan Zhiming, as saying the lab strictly implements bio-security procedures that would prevent the release of any pathogen.

"I would like to point out again that the origin of the virus is a complex scientific issue, and it should be studied by scientists and professionals," Geng said.

Geng also criticized US politicians who have suggested China should be held accountable for the global pandemic, saying they should spend their time on "better controlling the epidemic situation at home."

But a Chinese government spokesman, Zhao Lijian, demonstrated that China was not above sowing confusion in the face of the pandemic. He tweeted in March the falsehood that the virus might have come from the US Army.

Reported with AAP and the Associated Press