Omicron poses very high global risk: WHO

No Omicron-linked deaths had yet been reported, though further research was needed to assess its potential to escape protection against immunity induced by vaccines and previous infections, it added.

In anticipation of increased case numbers as the variant, first reported last week, spreads, the U.N. agency urged its 194 member states to accelerate vaccination of high-priority groups and ensure plans were in place to maintain health services.

Tedros Adhanom Ghebreyesus, WHO director-general, sounded the alarm at the start of an assembly of health ministers that is expected to launch negotiations on an international agreement on preventing future pandemics.

"The emergence of the highly mutated Omicron variant underlines just how perilous and precarious our situation is," Tedros said.