The United Kingdom (UK) has added six southern African countries to its red list, with flights being temporarily banned to those countries.
UK Health Secretary Sajid Javid said from 12:00 GMT on Friday six countries; South Africa, Namibia, Zimbabwe, Botswana, Lesotho and Eswatini would be added to the red list.
These measures follow the detection of a new Coronavirus variant in South Africa.
One expert described the variant, known as B.1.1.529, as “the worst one we’ve seen so far”, and there is concern it has the potential to evade immunity.
No cases have been confirmed in the UK.
The new variant has already been detected in South Africa's most populated province, Gauteng, where Johannesburg and Pretoria are located.
South Africa's Health Minister Joe Phaahla speaking at a press conference said the variant, B.1.1.529, is behind an “exponential” increase in reported cases in the country.
“[It] is now a variant of serious concern which driving the spike in numbers,” he said.
Scientists say B.1.1.529 has at least 32 spike protein mutations that could help it evade the body's immune response and make it more transmissible.
Director of Clinical Operational Research Unit at University College London (UCL) and a leading UK expert on COVID-19, Christina Pagel, called the new variant “extremely worrying.”
“Although the data are limited, our experts are working overtime with all the established surveillance systems to understand the new variant and what the potential implications could be,” said Adrian Puren, acting executive director of South Africa's National Institute for Communicable Diseases.
Francois Balloux, Director at the UCL Genetics Institute, said in a statement to the Science Media Centre the variant could be present in other parts of Africa.