"Countries should not cede authority to WHO," Musk, whose Twitter account has more than 132 million followers, wrote in response to a video of right-wing Australian senator Malcolm Roberts criticizing the organization.

"Countries aren't ceding sovereignty to @WHO," Director-General Tedros Adhanom Ghebreyesus tweeted in response. "The #PandemicAccord won't change that. The accord will help countries better guard against pandemics," he added.

In separate comments at the WHO's weekly news conference later on Thursday, Tedros said the claim that the pandemic treaty would see countries relinquish power to the WHO was "quite simply false" and "fake news."

"If any politician or businessperson, or anyone at all is confused about what the pandemic accord is and isn't, we would be more than happy to discuss it and explain it," Tedros said, in an apparent reference to Musk's comments.

Since COVID-19 first emerged more than three years ago, the World Health Organization has complained of an "infodemic" of misinformation and disinformation around the pandemic.

At times the U.N. agency has been the direct target of such attacks, with some commentators accusing it of seeking to wrest health policy away from governments, especially since international negotiations between member states began over a new pandemic treaty to avoid and deal with future outbreaks.

The WHO is made of 194 member states which take major decisions on its health policies and budgets through an annual assembly attended by governments.