European countries have imposed new restrictions on travel to and from Britain amid warnings a new coronavirus strain is “out of control”.

Millions of people had their Christmas holiday plans disrupted when the British government tightened COVID-19 restrictions for London and south-eastern England with the introduction of a Tier 4 lockdown.

Health Secretary Matt Hancock said the COVID-19 variant, which prompted the renewed lockdown, was “out of control” and spreading faster than other strains.

“All of the different measures we have in place, we need more of them to control the spread of the new variant than we did to control the spread of the old variant,” he told Sky News on Monday morning (Australian time).

More than 16 million Britons are required to stay at home under the new highest tier of restrictions, which came into force on Sunday.

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Although the new virus strain is not more dangerous than other strains, the restrictions might need to stay in place until vaccines could be rolled out, Mr Hancock said.

“Given how much faster this new variant spreads, it’s going to be very difficult to keep it under control until we have the vaccine rolled out,” he said.

“Everybody needs to behave as if they may well have the virus and that is the way that we can get it under control and keep people safe.”

Prime Minister Boris Johnson said the mutated strain was believed to be up to 70 per cent more contagious than the original COVID strain.

There is no evidence the strain is more deadly than others but experts are concerned about how quickly it is spreading. The World Health Organisation is monitoring local studies on how the variant behaves.

The WHO’s senior emergency officer for Europe, Catherine Smallwood, has confirmed the variant has been found in other countries.

There have been nine cases reported in Denmark and one case in the Netherlands, Dr Smallwood said.

One case has also been reported in Australia.

British cases spike

Britain has reported another 27,052 new COVID-19 cases, taking its total to over two million.

Another 534 people died, taking the official toll to more than 67,000.

Belgium has announced it will close its borders to trains and planes coming from Britain, while the Netherlands and Italy also suspended flights.

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Belgian Prime Minister Alexander De Croo said the ban on incoming travel from Britain covered flights and Eurostar train services, and would last at least 24 hours from midnight on Sunday, broadcaster VRT said.

Belgium was also in touch with neighbour France over road transit passengers from Britain, VRT said.

In Italy, Foreign Minister Luigi Di Maio announced plans to halt flights to and from Britain.

“Our priority is to protect Italy and our compatriots,” he said.

The Netherlands banned flights carrying passengers from Britain from Sunday. The restrictions will run until at least January 1, the Dutch government said.

It is monitoring developments and considering additional measures regarding other modes of transport.

Germany might also impose restrictions on flights from Britain and South Africa – which has also detected a new coronavirus strain – a health ministry official said.

Austria is also planning to ban flights from Britain and Scotland has imposed a ban on travel to the rest of the United Kingdom.

Spain said that, in response to the moves by some of its European Union partners, it had asked the European Commission and the European Council for a coordinated community response to the situation.

Otherwise it would act unilaterally to defend its interests and citizens, the Madrid government said.

-with AAP