China has accused the World Health Organisation (WHO) of "attempting to smear" Beijing after the global health body's boss said data linking the origins of coronavirus to raccoon dogs should have been shared years ago.
Samples of genetic material collected at a market in Wuhan - where the first cases were detected in late 2019 - showed DNA from raccoon dogs mingled with the virus.
Last month the WHO's director-general, Tedros Adhanom Ghebreyesus, said the newly disclosed genetic material "should have been shared three years ago".
Chinese health officials defended their search for the source of the virus, branding the WHO chief's remarks as "offensive and disrespectful".
Shen Hongbing, director of the China Centre for Disease Control and Prevention, said the WHO was "attempting to smear China" and should avoid helping others "politicise COVID-19".
"As a responsible country and as scientists, we have always actively shared research results with scientists from around the world," he said at a news conference.
The origins of the outbreak are still being debated and have become the focus of bitter political disputes.
Many scientists believe the virus jumped from animals to humans at the Huanan seafood market in Wuhan, the location of the first known COVID outbreak.
However, there have been suggestions it came from a lab leak in the city, which houses several laboratories - including China's top facility for collecting viruses.
The ruling Communist Party has tried to deflect criticism of its handling of the outbreak by spreading uncertainty about its origins, with officials repeating anti-US conspiracy theories the virus was created in Washington and smuggled into China.
The government has also said the virus may have entered China on mail or food shipments - though scientists have seen no evidence to support that theory.
Chinese officials initially suppressed information about the Wuhan outbreak in 2019 and punished a doctor who warned others of the new disease.
The ruling party reversed course in early 2020 and shut down access to major cities and international travel in a futile attempt to contain the disease.
The genetic material the WHO referred to was uploaded to a global database recently but collected in 2020 at the Wuhan market where wildlife was sold.
Scientists said it adds to evidence for the hypothesis coronavirus came from animals rather than a lab leak - though it does not resolve the question of where it started. They said the virus might have spread to raccoon dogs from humans.
Last month the director of the FBI said the agency believes COVID-19 "most likely" came from a lab leak in China, though four other US agencies, along with a national intelligence panel, still believe the pandemic was likely the result of natural transmission, while two are undecided.
The information was removed by Chinese officials from the database after foreign scientists asked the CDC about it, but it had been copied by a French expert and shared with researchers outside of China.
Mr Shen said scientists investigated the possibility of a lab leak and "fully shared our research and data without any concealment or reservation".
He said the source of COVID-19 had yet to be found but noted it took years to identify the AIDS virus and its origins are still unclear.
"Some forces and figures who instigate and participate in politicising the traceability issue and attempting to smear China should not assume that the vision of the scientific community around the world will be blinded by their clumsy manipulation," Mr Shen said.