Europe rushed to ban travel from southern Africa on Friday to slow the spread of a new Covid-19 strain that scientists fear could torpedo efforts to beat the pandemic.

Global markets plunged as news sank in that a new variant more infectious than the Delta and possibly more resistant to vaccines could potentially deal a heavy blow to the global recovery.

Scientists are now racing to determine the characteristics and threat of the heavily mutated strain, designated B.1.1.529.

Belgium said Friday it has detected the first announced case in Europe of the new Covid-19 variant, in an unvaccinated person returning from abroad.

The World Health Organization (WHO) said it could take several weeks to understand the variant and cautioned against imposing new travel curbs.

"WHO recommends that countries continue to apply a risk based and a scientific approach when implementing travel measures... implementing travel measures is being cautioned against," said spokesman Christian Lindmeier.

Europe is already struggling to cope with a fresh coronavirus surge, and returning restrictions have sparked rioting in some countries.

Austria, the Czech Republic, Germany, Italy and the Netherlands on Friday joined Britain in announcing travel bans.

The bans all included South Africa, and in many cases also some or all of the following: Botswana, Eswatini (Swaziland), Lesotho, Namibia, Zambia and Zimbabwe.

The EU commission said it would swiftly coordinate joint action among the bloc's 27-member states.

"The last thing we need now is an introduced new variant that causes even more problems," Germany's acting health minister Jens Spahn said as his country battled a ferocious fourth wave of the pandemic.

'Many mutations'

The rush to close off southern Africa comes a day after scientists in Johannesburg said they had detected the new strain with at least 10 mutations, compared with two for Delta.

The variant was of "serious concern" and had been blamed for a surge in infection numbers, authorities in South Africa said Thursday.

It had also been detected in Botswana and Hong Kong among travellers from South Africa.

Israel said it had quarantined three people, all vaccinated, identified with the new variant, with one having just returned from Malawi.

The WHO said it was "closely monitoring" the variant and weighing whether it should be designated a variant of "interest" or of "concern".

It was also up to WHO to decide whether to give the strain a name taken from the Greek alphabet, as for previous major variants such as Delta.

Spooked by the variant, the European markets fell over three percent, with airline shares especially hit. Tokyo closed down 2.53 percent, after having lost more than three percent in the middle of the day.

The new variant erupted onto the scene as European countries announced new measures to face the ravages of the Delta variant that is again bringing a critical shortage of beds in hospitals.

Germany, the Czech Republic and Portugal -- which has one of the world's highest vaccination rates -- all announced new measures in recent days to stem a tide of infections that has been worse than feared.

Authorities in the Netherlands were bracing for new riots ahead of an expected announcement Friday by Prime Minister Mark Rutte to tighten a partial lockdown as infections reach record levels.

Belgium, which saw similar scenes of violence last weekend, is also expected to announce new measures.

In a sign that the new spike was crushing hopes of a slow return to normalcy, EU council chief Charles Michel cancelled a visit to Japan and South Korea due to a positive case among his cabinet in Brussels.

10 mutations

Scientists said the new variant has at least 10 mutations, compared to two for Delta and three for Beta.

"The concern is that when you have so many mutations, it can have an impact on how the virus behaves," Maria Van Kerkhove, the WHO's technical lead on Covid-19, said at a virtual press briefing.

"It will take a few weeks for us to understand what impact this variant has on any potential vaccines," she added.

Neutralising the variant is "complicated by the number of mutations this variant" contains, said one of the South African scientists Penny Moore.

"This variant contains many mutations that we are not familiar with," she added.

The Africa Centres for Disease Control and Prevention said it will soon meet South African experts to discuss the variant.

"There are so many variants out there but some of them are of no consequence on the trajectory of the epidemic," Africa CDC head John Nkengasong told a news conference on Thursday.

No carnival for Brazil

In Asia, China's strict zero-Covid policy pushed Shanghai to cancel hundreds of flights and close some schools after three local cases were recorded, health officials said Friday.

"China has accumulated lots of experience in 'dynamic zero-Covid'," said Zhang Wenhong, head of the Shanghai Covid prevention expert task force, at a Thursday briefing.

The Philippines said Friday it would welcome back next week vaccinated foreign tourists from countries designated as low-risk.

But the effects of the pandemic have pushed even the most hardened sceptics on the world stage to embrace some anti-virus measures.

"As far as I'm concerned, we shouldn't have carnival" in February, said Brazilian President Jair Bolsonaro.