JERUSALEM • Israel will ban the entry of all foreigners into the country from today, making it the first country to shut its borders completely in response to a new and potentially more contagious coronavirus variant.

It added that it would use counter-terrorism phone-tracking technology to contain the spread of the Omicron variant.

The discovery of the variant has sparked global concern, a wave of bans on travellers from some parts of Africa and a plunge in financial markets as investors fear the new variant will halt the global recovery from the nearly two-year-old pandemic.

The World Health Organisation has classified Omicron - first detected in South Africa - as a variant of concern, though it has cautioned nations not to hastily impose travel curbs, saying they should take a "scientific and risk-based approach".

Israel's Prime Minister Naftali Bennett said in a statement on Saturday that the ban, pending government approval, would last 14 days.

Officials hope that within that period, more information will emerge on how effective Covid-19 vaccines are against Omicron.

"Our working hypotheses are that the variant is already in nearly every country and that the vaccine is effective, although we don't yet know to what degree," Interior Minister Ayelet Shaked told N12 News.

Israelis entering the country, including those who are vaccinated, will be required to undergo quarantine, Mr Bennett said.

The Shin Bet counter-terrorism agency's phone-tracking technology will be used to locate carriers of the new variant to curb its transmission to others, Mr Bennett said.

Used on and off since March last year, the surveillance technology matched virus carriers' locations against other mobile phones nearby to determine with whom they had come into contact.

Israel's move came as Omicron fears sparked a raft of new measures around the world.

In Britain, tougher entry rules for all arriving passengers as well as the return of a mask mandate were announced, after the country confirmed its first two cases of the new Omicron strain.

Both cases were linked to travel from southern Africa, and the government on Saturday also expanded travel restrictions on the region with the addition of four countries to a "red list".

Prime Minister Boris Johnson said face masks would again be required in shops and on public transport, after controversially ditching the mandate in July, when he reopened the British economy after a prior nationwide lockdown.

He signalled that there will be no new lockdown for now, vowing a review of the new measures in three weeks and expressing hope that Britons could look forward to a more festive Christmas than last year.

"But we now need to go further and implement a proportionate testing regime for arrivals from across the whole world," Mr Johnson told a hastily arranged news conference, hours after the government confirmed the two Omicron cases.

"So we are not going to stop people travelling... but we will require anyone who enters the United Kingdom to take a PCR (polymerase chain reaction) test by the end of the second day after their arrival, and to self-isolate until they have a negative result," he said.

Currently, all Britons and foreigners entering the United Kingdom are required to take a PCR test on day two after their arrival.

The new rules add the requirement for isolation pending a negative result, significantly toughening the regime, in a bid to curb the spread of the new strain.

Tourist haven the Maldives said yesterday that it was barring travellers from seven African countries over concerns about the new coronavirus variant.

Travellers will not be allowed into the Maldives from South Africa, Botswana, Zimbabwe, Mozambique, Namibia, Lesotho and Eswatini, the Health Ministry said in a statement.

In Mexico, Deputy Health Secretary Hugo Lopez Gatell called the measures taken by some countries "disproportionate". "It (Omicron) has not been shown to be more virulent or to evade the immune response induced by vaccines. They (the measures) affect the economy and well-being of people," he said in a Twitter post on Saturday.

REUTERS, AGENCE FRANCE-PRESSE