The European Commission has recommended EU countries introduce an "emergency brake" on travel from southern Africa after a new COVID variant was detected there.

Commission President Ursula von der Leyen said the bloc must "act very swiftly" as the first infection of the new strain was detected in Belgium on Friday afternoon.

The new B.1.1.529 variant, first detected in Botswana, has sparked alarm among scientists due to its high number of mutations. It has also been found in Belgium, Israel and Hong Kong, with the Hong Kong case a traveller from South Africa.

"All air travel to these countries should be suspended until we have a clearer understanding about the danger posed by this new variant," Ms von der Leyen told reporters.

"Travelers returning from this region should respect strict quarantine rules."

"It is now important that all of us in Europe act very swiftly, decisively and united," she added, in calling for EU citizens to get vaccinated and improve their protection with booster jabs.

Meanwhile, health authorities in Belgium said the new infection had been traced to an unvaccinated young woman who had developed mild flu-like symptoms 11 days after travelling to Egypt from Turkey.

Belgian virologist Marc van Ranst said the patient did not report any links to South Africa or other neighboring high-risk countries.

Health secretary Sajid Javid said the variant was of "huge international concern" but confirmed no cases had yet been detected on UK soil. On Thursday, ministers announced a ban on all travel from the six affected countries in southern Africa.

"We are concerned that this new variant may pose a substantial risk to public health," Javid told MPs. "The variant has an unusually large number of mutations."

Professor Adam Finn, a member of the Joint Committee on Vaccination and Immunisation, told Britons to brace for the possible return of restrictions this Winter.

(With input from agencies)