Omicron, dubbed a “variant of concern” by the World Health Organisation, was discovered in South Africa and has since been detected in Belgium, Botswana, Israel and Hong Kong.
A minister in the German state of Hesse said the variant had very probably arrived in Germany in a traveller returning from South Africa.
The WHO convened a global meeting on international measures to defeat the virus. Comprising all 194 members of the World Health Assembly, it was called to develop a new accord on the pandemic response.
On Saturday, the UAE issued restrictions for travellers departing from or transiting through Botswana, Eswatini, Lesotho, Mozambique, Namibia, South Africa and Zimbabwe. Those travellers will not be accepted for travel into Dubai until further notice.
“We will have more pandemics in the future. The question is not if, but when,” Jaouad Mahjour, the WHO assistant director general for emergency preparedness, told reporters.
WHO chief Dr Tedros Adhanom Ghebreyesus wants a treaty to end what he said was "neglect and panic”.
"The ongoing chaos of this pandemic only underlines why the world needs an iron-clad global agreement to set the rules,” he said.
Financial markets plunged on Friday, with stocks of airlines and others in the travel sector hit particularly hard.
Investors said they were worried the variant could cause another surge in the pandemic and stall a global recovery. Oil prices tumbled by about $10 a barrel.
Epidemiologists say travel curbs may be too late to stop Omicron from circulating globally. But on Friday, a string of countries, including the US, Brazil, Canada and EU member states, announced travel bans or restrictions on arrivals from southern Africa.
On Saturday, Australia said it would bar entry of non-citizens who have been in one of nine southern African countries and would impose supervised 14-day quarantines for Australian citizens and their dependents returning from any of these nations.
Japan said it would extend its tightened border controls to three more African countries after imposing curbs on travel on Friday. Sri Lanka, Thailand and Oman also announced travel curbs on southern African nations.
Many countries in Europe are already battling a surge in Covid-19 infections. Some have reintroduced restrictions on social activity to curb the spread.
In Britain, the main opposition Labour Party called on Saturday for the vaccine booster programme to be accelerated. It said the gap between the second dose of a vaccination and the booster dose should be cut from six to five months.
“This new variant is a wake-up call,” Labour's junior health spokesman, Alex Norris, said. “The pandemic is not over. We need to urgently bolster our defences to keep the virus at bay.”
Some experts say it could be some time before the risk posed by the new variant becomes clear.
“I certainly thought [of] Delta as a peak variant, and probably it couldn’t get much worse than that. This looks potentially worse,” said Danny Altmann, professor of immunology at Imperial College London.
“On the other hand, there’s no reporting from South Africa yet that cases are more severe, and it looks like vaccines may still be doing something because we heard there yesterday that the people in hospital tended to be the unvaccinated people rather than the vaccinated.”