A growing number of nations have halted air travel from Britain, while France banned British trucks for 48 hours from Sunday evening while the more infectious variant is assessed.

British Health Secretary Matt Hancock said the strain is "out of control" around London and southeast England, where a new Tier 4 level of lockdown was introduced on Saturday.

There were rising hopes that France would soon allow traffic to flow again, if truck drivers took coronavirus tests on arrival.

While the French ban does not prevent trucks from heading for Britain, the move stoked worries about shortages at a time of year when Britain produces very little of its own food and relies heavily on produce delivered from Europe by truck.

In a sign of the government's concern, Prime Minister Boris Johnson called a meeting of the government's emergency committee.

Around 10,000 trucks pass through Britain's port of Dover every day, accounting for about 20 per cent of the country's trade in goods.

British Transport Secretary Grant Shapps said France's ban was "slightly surprising" but insisted the UK public will "for the most part" not notice any shortages.

Supermarket chain Sainsbury's warned that some products, such as lettuce, cauliflower, broccoli and citrus fruits, could soon be in short supply if the crisis not resolved in the coming days.

France's Minister of Transport Jean-Baptiste Djebbari indicated that a solution was coming.

In a tweet, he said that "in the coming hours, at a European level, we will put a solid health protocol in place so that the flow from the United Kingdom can resume".

Canada, India, France, Germany, Italy, Spain and Poland were among the countries that halted flights from Britain.

In the US, New York governor Andrew Cuomo said he wanted a ban on flights from Britain to New York City.

Eurotunnel, the rail operator that carries passengers and freight between Britain mainland Europe, has suspended service out of the UK.

The moves come in the wake of Johnson's announcement on Saturday that he was placing London and the southeast of England in a newly created tier of restrictions after scientific advisers warned that they had detected a new strain of the virus that may be more contagious.

Johnson said early indications are that the variant is 70 per cent more transmissible and is driving the rapid spread of infections in the capital and surrounding areas.

The European Centre for Disease Prevention and Control said that while preliminary analysis suggests the new variant is "significantly more transmissible" there is no indication that infections are more severe.

The Stockholm-based agency said a few cases of the variant have been reported by Iceland, Denmark and the Netherlands. It also cited news reports of cases in Belgium and Italy.

Australian Associated Press