More than 200 British skiers fled a coronavirus quarantine in the popular Swiss resort of Verbier on Saturday night, reports say.
A spokesman in Valais canton said 420 British guests had booked into Verbier accommodation before Christmas and now only about a dozen were left.
Switzerland imposed a 10-day quarantine backdated to 14 December because of the new virus strain spreading in the UK.
The country also stopped flights from the UK and South Africa on 20 December.
Some Swiss hoteliers only discovered the guests had vanished when room service trays were left untouched outside doors, Swiss media reported. Others were called by British tourists demanding their money back once they had safely crossed into France, the BBC's Imogen Foulkes reports from Geneva.
Verbier is especially popular among the British, who normally make up about one-fifth of the resort's winter clientele.
Switzerland caused controversy by deciding, despite the pandemic, to keep its ski resorts open.
Some Swiss believe that decision was a mistake, our correspondent reports. Others are angry, as for decades the British have been enthusiastic winter visitors to Switzerland, but now feel the tourists have abused the hospitality offered to them.
Scientists say the new Covid-19 strain first spotted in the UK is more infectious than the one responsible for the pandemic, but not necessarily any more dangerous for those infected.
The new variant has already been detected in Switzerland and several other countries. Another new variant emerged in South Africa this month and has spread elsewhere.
Some sympathy for Brits
The spokesman for Bagnes, an area of Valais containing Verbier, voiced understanding for the departed British.
"We understand their anger," Jean-Marc Sandoz told the SonntagsZeitung. "Suddenly families with small children were locked into 20 sq m (215 sq ft), and that's intolerable."
Ski resorts were crowded in neighbouring Austria at the weekend, but Austria's quarantine means that very few foreign tourists have travelled there. For locals too the options are limited, as hotels and restaurants are shut, and social distancing has reduced the cable car and train services.
There were long queues of traffic outside some Austrian resorts, forcing car parks to close early. Ski lifts were only able to take about half the normal numbers, because of social distancing, and Covid masks were obligatory. Resorts close to Salzburg were less crowded, broadcaster ORF reported.
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Despite the sympathy voiced by Mr Sandoz, there were some angry tweets condemning the British tourists for slipping out of quarantine under cover of darkness.
Britain's reputation hasn't been trashed enough this week, so let's add the story of 200 British tourists who had been quarantining in Verbier doing a runner in the middle of the night. Charming. https://t.co/YlPoClcZ4a— Mary Novakovich (@mary_novakovich) December 27, 2020
Mr Sandoz said the new coronavirus quarantine had made it "the worst week our community has ever experienced".
The Swiss health ministry, quoted by AFP news agency, said on Sunday two cases of the British Covid-19 variant had been detected in Switzerland and one in neighbouring Liechtenstein. It also said there were two Swiss cases of the South African variant.
Ski resorts in France, Italy and many other countries are closed to tourists this season - a devastating blow to their income.
At the start of the pandemic in Europe the Austrian ski resort of Ischgl was identified as a virus hotspot, and an official report, published in October, deplored errors which had allowed thousands of tourists to get infected.
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