China hit out at the "dark history" of the US intelligence community Thursday, after President Joe Biden ordered a probe into the Covid-19 origins as the lab-leak theory rebounds and strains relations between the two countries.

President Biden on Wednesday ordered US intelligence agencies to report to him in the next three months on whether the Covid-19 virus first emerged in China from an animal source or from a laboratory accident.

The lab-leak theory, initially dismissed as "highly unlikely" by a delayed World Health Organization mission to China, has resurfaced in recent days, driven by Washington.

China wholly rejects the theory the virus may have emerged from a virology lab in Wuhan and has instead accused the US of peddling conspiracies and politicising the pandemic to divert attention from the high death rates there.

Rejecting the need for a new investigation into the pandemic, a ministry of foreign affairs spokesman on Thursday said the Biden administration's "motive and purposes are clear".

"The dark history of the US intelligence community has long been known to the world," Zhao Lijian added, referring to the US' unfounded allegations of weapons of mass destruction which justified its invasion of Iraq.

According to Biden, intelligence agencies are currently split over the two possible sources for the virus that swept the planet over the past year, killing more than 3.4 million people -- a figure experts say is undoubtedly an underestimate.

Biden's order signals an escalation in mounting controversy over how the virus first emerged -- through animal contact at a market in Wuhan, China, or through release of the coronavirus from a highly secure research laboratory in the same city.

The idea is gaining increasing traction in the United States, where it was initially fueled by Trump and his aides and dismissed by many at the time as a political stunt.

Citing a US intelligence report, The Wall Street Journal reported Sunday that a trio from the Wuhan Institute of Virology were hospitalised with a seasonal illness in November 2019, a month before Beijing disclosed the existence of a mysterious pneumonia outbreak.

The natural origin hypothesis -- backed as the most likely by the WHO expert team who visited China -- holds that the virus emerged in bats then passed to humans, likely via an intermediary species.

This theory was widely accepted at the start of the pandemic, but as time has worn on, scientists have not found a virus in either bats or another animal that matches the genetic signature of SARS-CoV-2.