The head of the World Health Organisation has said he is "very disappointed" China has denied its experts access to investigating the origins of coronavirus.

A ten-strong team of international scientists and virologists had been due to set off in early January as part of a long-awaited mission to probe early cases of coronavirus, first reported over a year ago in China's Wuhan province.

But Chinese officials have not yet finalised the necessary permissions for the team to enter the country, despite the WHO having been talking with Chinese officials since July.

And in a rare criticism of Beijing, WHO Director-General Tedros Adhanom Ghebreyesus, expressed his frustration at the delay.

"Today, we learned that Chinese officials have not yet finalized the necessary permissions for the team's arrival in China.

"I'm very disappointed with this news, given that two members had already begun their journeys and others were not able to travel at the last minute, but had been in contact with senior Chinese officials," he said.

Mr Tedros has spoken with unspecified senior Chinese officials, and "fully impressed upon them the absolute critical nature of this".

He said he had "made it clear" that the mission was a priority for the UN health agency, adding: "We are eager to get the mission under way as soon as possible."

Members of the international scientific team began departing from their home countries over the past 24 hours as part of an arrangement between WHO and the Chinese government.

The experts drawn from around the world are expected to visit the city of Wuhan, which is where the coronavirus first emerged over a year ago. Scientists have long said it is essential to find out how the virus jumped species into humans.

It has been reported the Chinese government has been strictly controlling all research at home into the origins of the virus and state-owned media have played up reports that suggest the virus could have originated elsewhere.

Chinese Foreign Minister Wang Yi said recently that "more and more research suggests that the pandemic was likely to have been caused by separate outbreaks in multiple places in the world".

The UN health agency came in for searing criticism from President Donald Trump and other US officials over its alleged deference to and excessive praise of China's handling of the initial outbreak.

Ahead of the trip, China has been seeking to shape the narrative about when and where the pandemic began, with senior diplomat Wang Yi saying "more and more studies" showed that it emerged in multiple regions.

China has reported a total of 96,310 cases with 4,787 deaths, according to Johns Hopkins University.

Hospitals are currently treating 443 people for the disease while another 363 people are being observed in isolation for being suspected cases or for testing positive without showing symptoms.