The new Covid-19 Omicron variant poses a "very high" risk globally, the World Health Organization warned Monday, stressing that uncertainties remained about how contagious and dangerous the strain was.

"If another major surge of Covid-19 takes place driven by Omicron, consequences may be severe," WHO said in a technical note, adding though that "to date, no deaths linked to Omicron variant have been reported."

The World Health Organization on Friday declared the recently-discovered B.1.1.529 strain of Covid-19, first detected in southern Africa, to be a variant of concern and renamed it Omicron.