As the new strain of COVID-19 Omicron is being studied, nations are imposing travel curbs on South Africa, where the variant was first reported.

President Joe Biden announced on Friday that the U.S. would restrict arrivals from South Africa and nearby countries from next Monday. American nationals and permanent residents are not subject to this measure.

The European Union said its 27 member states have agreed on similar restrictions. Britain and Russia have also announced a ban on flights and arrivals from South Africa and its vicinity.

Asian, Middle Eastern and South American nations are also introducing border controls, while Australia is known to be considering mandatory quarantine of travelers from South Africa.

South Africa's Health Minister Joe Phaahla has slammed the travel restrictions as unjustified, saying they completely go against the norms and standards advised by the World Health Organization.

The WHO said it will take weeks to analyze the full impact of the new variant. 

Vaccine producers are also reviewing whether a new vaccine would be necessary to deal with the new variant known as Omicron.