GENEVA - 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.

The classification puts Omicron into the most-troubling category of Covid-19 variants, along with the globally-dominant Delta, plus its weaker rivals Alpha, Beta and Gamma.

Nations rushed to ban flights to slow the spread of Omicron on Friday, while stock markets and oil prices plunged on fears surrounding the variant, potentially dealing a heavy blow to the global economic recovery.

"Based on the evidence presented indicative of a detrimental change in Covid-19 epidemiology... the WHO has designated B.1.1.529 as a variant of concern (VOC), named Omicron," the UN health agency said in a statement.

The WHO said it could take several weeks to complete studies of Omicron to see if there are any changes in transmissibility, severity or implications for Covid vaccines, tests and treatments.

AFP