No cases of the new COVID variant have been detected in the UK, but it is highly likely it has now spread beyond southern Africa, the health secretary has said.
Sajid Javid warned the new strain could be more transmissible than the Delta variant and there is a "possibility it might have a different impact on individuals" who get the virus.
He said the UK remains in a "strong position" due to the high vaccination take-up but said the new variant, named B.1.1.529, first detected in South Africa, has an "unusually large number of mutations".
Soon after he spoke in the Commons, Europe confirmed its first case of the variant after it was detected in Belgium. It involved an unvaccinated person who had travelled from abroad. They developed symptoms and tested positive on 22 November.
Flights from South Africa and five other southern African countries, Namibia, Lesotho, Botswana, Eswatini and Zimbabwe have been suspended from 12pm today until 4am on Sunday.
From Sunday onwards, new arrivals of UK and Irish residents into the UK from those nations will be required to quarantine in hotels after they were placed on the red list on Thursday night.
Non UK and Ireland residents will not be allowed in from those countries.
And European Union states have agreed to suspend temporarily travel to southern Africa after the detection of the new variant, the presidency of the EU has said. An EU source said the restrictions would apply to the six nations.
However, South African health minister Joe Phaahla warned the decision of other countries to impose travel restrictions was "unjustified", but he did admit preliminary studies suggest the variant may be more transmissible.
Mr Phaahla said the "knee-jerk" reaction of many nations "really doesn’t make sense", adding that many countries which have taken action are themselves battling new waves.
He said the UK imposed restrictions without consulting South Africa, saying: "It was a unilateral action."
Mr Javid said the variant "may also impact the effectiveness of one of our major treatments, Ronapreve", an antibody treatment being used in the NHS.
He said: "There are no detected cases of this variant in the UK at this time. But this new variant is of huge international concern."
He said the UK was the first country to identify "the potential threat of this new variant and to alert international partners".
"Further cases have been identified in South Africa and in Botswana, and it is highly likely that it has now spread to
other countries," he added.
The new variant was detected in Hong Kong in a passenger from South Africa who was fully vaccinated and authorities there notified the South African authorities.
They had come from Gauteng province, home to Johannesburg and Pretoria, where Mr Javid said about 80% of cases tested with a PCR test "have shown something that is known as the S-gene drop out which we associate with this variant".
Mr Javid said South Africa has experienced "exponential growth", with cases increasing fourfold over the past two weeks.
He said it is not yet definitive but does indicate "there could be many more cases of this new variant than just those that have been sequenced".
South Africa saw just over 200 new confirmed cases per day in recent weeks, rising to 2,465 on Thursday. Scientists say the new variant could explain the rise, but that is not certain.
The MP told the Commons the variant has many features of Alpha, Beta and Delta strains but it is not yet known if it causes more severe illness.
Getting a booster jab, when eligible, is even more important now, he added.
Vaccine producer Pfizer said in a statement it should be able to tweak its supply to deal with a new any variant in around 100 days, should it become necessary.
The health secretary was making a statement to the Commons an hour before travel restrictions were brought in for six southern African countries.
Several other countries have also restricted travel from those six African nations and more are announcing restrictions as Friday goes on.
Mr Javid confirmed the government is still following Plan A for managing COVID-19 this autumn and winter but warned "if we need to go further, we will".
© Sky News 2021