The World Health Organization said on Friday that the second stage of an investigation into the origins of COVID-19 should include further studies in China and lab audits with WHO chief Tedros Adhanom Ghebreyesus proposing five priorities for the next phase of the investigation

The 5 points proposed by the WHO chief to the member states included "audits of relevant laboratories and research institutions operating in the area of the initial human cases identified in December 2019", AFP reported, quoting a copy of his opening statement provided by the WHO.

The UN health agency has been under intensifying pressure for a new, more in-depth investigation of how the disease that has killed over four million people around the world first emerged.

The WHO chief also suggested investigators should focus on "studies prioritising geographic areas with the earliest indication of circulation of SARS CoV-2", the virus that causes COVID-19 and called for more studies of animal markets in and around the Chinese city of Wuhan, where the disease was first detected.

The WHO team of independent, international experts went to Wuhan in January this year, more than a year after COVID-19 first surfaced in the city in late 2019, to help Chinese counterparts probe the pandemic origins. The experts published a report in late March, but it was unable to draw any firm conclusions about how the virus first jumped to humans.

Instead they ranked several hypotheses according to how likely they believed they were, finding that it was most likely the virus jumped from bats to humans via an intermediate animal. An alternative theory involving the virus leaking from a laboratory was deemed "extremely unlikely".

The investigation faced criticism for lacking transparency and access, and for not evaluating the lab-leak theory more deeply.

Long derided as a right-wing conspiracy theory, and vehemently rejected by Beijing, the idea that COVID-19 may have emerged from a laboratory leak has been gaining momentum.

The WHO has now developed a protocol for evaluating laboratory safety and biological security to help ascertain whether the virus may have emerged due to a lab accident, AFP reported.

The protocol, which the agency aims to use to investigate the COVID-19 origin as well as possible future outbreaks, provides measures for evaluating, among other things, the storage of virus samples and handling of waste.