New cases were confirmed in Australia, Germany, UK and Italy, while Israel closes its borders to all foreigners in a bid to stem the spread of the new Omicron variant of the coronavirus.
The new potentially more contagious Omicron variant of the coronavirus has popped up in more countries, just days after being identified in South Africa.
Health officials in Australia said on Sunday they had detected the Covid Omicron strain for the first time after testing two passengers from southern Africa who flew into Sydney.
New cases were also confirmed in Germany, UK and Italy on Saturday, while Dutch authorities quarantined 61 passengers from South Africa who tested positive for Covid-19.
Israel is to close its borders to all foreigners later on Sunday, making it the first country to shut its borders completely in a bid to stem the spread of the new variant, authorities said.
Because of fears that the new variant has the potential to be more resistant to the protection offered by vaccines, there are growing concerns around the world that the pandemic and associated lockdown restrictions will persist for far longer than hoped.
Latest omicron cases
An Italian who had traveled to Mozambique on business landed in Rome on November 11 and returned to his home near Naples.
He and five family members, including two school-age children, have since tested positive, the Italian news agency LaPresse said. All are isolating in the Naples suburb of Caserta in good condition with light symptoms.
In Germany, the Max von Pettenkofer Institute, a Munich-based microbiology centre, said the omicron variant was confirmed in two travellers who arrived on a flight from South Africa on November 24.
And Dutch officials said the Omicron variant was "probably" among 61 passengers who had arrived on two flights from South Africa a day before and tested positive for Covid-19.
Global travel restrictions
Nearly two years since the start of the pandemic that has claimed more than 5 million lives around the world, countries are on high alert.
Many have already imposed travel restrictions on flights from southern Africa as they seek to buy time to assess whether the omicron variant is more transmissible than the current dominant delta variant.
Despite the banning of flights, there are mounting concerns that the variant has already been widely seeded around the world.
A number of pharmaceutical firms, including AstraZeneca, Moderna, Novavax and Pfizer, said they have plans in place to adapt their vaccines in light of the emergence of omicron.
Pfizer and its partner BioNTech said they expect to be able to tweak their vaccine in around 100 days.