Passengers arrive at the Eurostar terminal at Gare du Nord train station, Paris. They'll need to have a valid reason to visit from Saturday. /Reuters/Benoit Tessier/File Photo
France is banning travel from the UK without "compelling reasons" from December 18.
Leisure trips or non-urgent business will not be considered valid reasons for travel into France from Saturday.
The sudden move was announced on Thursday morning by the government spokesman Gabriel Attal. He said the aim of the new restrictions was to "tighten the net" to slow down the influx of new infections of the Omicron variant of COVID-19 coming in from the UK.
French residents and French citizens will be allowed to come in from Britain, but they must then isolate for a week in a place of their choice.
That seven-day quarantine can be reduced to 48 hours if they test negative after arrival.
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There are other exemptions on the list of those people who are allowed in from the UK, including hauliers, airport and seaport workers, healthcare staff, customs and border force agents, and students on a recognized academic course.
Everyone coming into France from the UK must also provide proof of a negative coronavirus test that is no older than 24 hours.
The new restrictions apply to everyone, including people who are fully vaccinated and those who have had a booster shot.
'Tidal wave' of Omicron cases forecast to hit the UK
The French government acted after the UK on Wednesday reported its highest number of new daily COVID-19 cases since the start of the pandemic in December 2019 – 78,610 infections were confirmed in the UK on December 15.
England's chief medical officer has warned that more coronavirus records will be broken.
On Sunday, UK Prime Minister Boris Johnson warned of a rapid acceleration in the number of new infections of the Omicron variant of the coronavirus.
"No one should be in any doubt: there is a tidal wave of Omicron coming," he said in a televised address.
France has had two successive days this week with more than 60,000 new cases confirmed.
Cover photo: People wearing face masks to protect against COVID-19 cross the Trocadero Plaza in Paris, Wednesday, December 15, 2021. /AP Photo/Michel Euler