Relatives of Wuhan's coronavirus dead on Wednesday said Chinese authorities have deleted their social media group and are pressuring them to keep quiet while a World Health Organization team is in the city to investigate the pandemic's origins.

Scores of relatives have banded together online in a shared quest for accountability from Wuhan officials who they blame for mishandling the outbreak that tore through the city one year ago.

The effort has thus far been thwarted by official obstruction, monitoring of social media groups and intimidation, say next-of-kin.

But pressure has escalated in recent days, apparently to muzzle any criticism and avoid embarrassment during the highly sensitive WHO investigation.

A group on social media platform WeChat used by 80 to 100 family members over the past year was suddenly deleted without explanation about 10 days ago, said Zhang Hai, a group member and a vocal critic of the outbreak's handling.

"This shows that (Chinese authorities) are very nervous. They are afraid that these families will get in touch with the WHO experts," said Zhang, 51, whose father died early in the pandemic of suspected Covid-19.

The WHO experts arrived in Wuhan on January 14 and are due to emerge from a 14-day quarantine on Thursday.

"When the WHO arrived in Wuhan, (authorities) forcibly demolished (the group). As a result we have lost contact with many members," Zhang added.

Other next-of-kin confirmed the group's deletion. WeChat is operated by Chinese digital giant Tencent. 

Popular platforms routinely censor content deemed objectionable by the government.

Same old tune

Relatives accuse the Wuhan and Hubei provincial governments of allowing Covid-19 to explode out of control by trying to conceal the outbreak when it first emerged in the city in December 2019, then failing to alert the public and bungling the response.

According to official Chinese figures, it killed nearly 3,900 in Wuhan, accounting for the vast majority of the 4,636 dead China has reported. 

Many next-of-kin distrust those numbers, saying the scarcity of testing in the outbreak's chaotic early days meant many are likely to have died without being confirmed as having the disease.

More than two million people have died so far globally.

While China has broadly controlled the pandemic on its soil, it has frustrated independent attempts to trace its origins.

Instead, it has sought to deflect blame for the horrific worldwide human and economic toll by suggesting, without proof, that it emerged elsewhere.

A team of WHO virus experts were finally allowed into Wuhan a fortnight ago.

Their highly watched probe into the virus origins is due to start on Thursday, under tight security.

Another family member, a retiree who says her adult daughter died of the virus last January, told AFP she was summoned last week by authorities and warned not to "speak to media or be used by others". 

Authorities came to her door on Tuesday "and sang the same old tune and gave me 5,000 yuan ($775) in a 'condolence payment'", she added, requesting anonymity.

Official obstruction

The Communist Party government smothers anything that reflects its governance in a poor light, and the early days of the outbreak remain among the most sensitive topics in China today.

Several Wuhan relatives have tried to file lawsuits seeking compensation and punishment of officials, but say courts have refused to accept them.

The Wuhan government has repeatedly failed to reply to AFP queries regarding the families and their demands.  

Zhang called on the WHO experts to "bravely" meet with next-of-kin, saying the investigators are likely to be misled or obstructed by Chinese authorities.

He said the families' hard-earned knowledge of how the virus played out could aid the investigation, though he acknowledges such a meeting is highly unlikely.

The virus is believed to have emerged from bats and to have initially spread from a wet market in Wuhan where wild animals were sold as food. 

But little else is known. 

Another theory, amplified by former US President Donald Trump, is that it leaked from a laboratory in Wuhan where researchers were studying coronaviruses.