Dozens of people are presumed dead and about 100 more are injured after a fire at a bar in the Swiss Alps during New Year's Eve celebrations.
Police say the blaze broke out at Le Constellation bar, in the exclusive Alpine ski resort municipality of Crans-Montana, about 1.30am on New Year's Day (11.30am AEDT).
"Several tens of people" are presumed dead and about 100 injured, most of them seriously, Valais Canton police commander Frédéric Gisler said.
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Work is under way to identify the victims and inform their families but "that will take time and for the time being it is premature to give you a more precise figure", Gisler said.
Beatrice Pilloud, attorney general of the Valais Canton, said it was too early to determine the cause of the fire. Experts have not yet been able to go inside the wreckage.
"At no moment is there a question of any kind of attack," Pilloud said.
Witnesses describe scenes like a horror film
Helicopters and ambulances rushed to the scene to assist victims, including some from different countries.
Two women told French broadcaster BFMTV that they were inside when they saw a barman carrying a barmaid on his shoulders. The barmaid was holding a lit candle in a bottle that set fire to the wooden ceiling. The flames quickly spread and collapsed the ceiling, they told the broadcaster.
One of the women described a crowd surge as people frantically tried to escape from a basement nightclub up a narrow flight of stairs and through a narrow door.
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Another witness speaking to BFMTV described people smashing windows to escape the blaze, some gravely injured, and panicked parents rushing to the scene in cars to see whether their children were trapped inside. The young man said he saw about 20 people scrambling to get out of the smoke and flames and likened what he saw to a horror movie as he watched from across the street.
Officials described how the blaze likely triggered the release of combustible gases that ignited violently and caused what English-speaking firefighters call a flashover or backdraft. The officials referred to it by the French "embrasement généralisé".
"This evening should have been a moment of celebration and coming together, but it turned into a nightmare," said Mathias Reynard, head of the regional government of the Valais Canton.
The injured were so numerous that the intensive care unit and operating theatre at the regional hospital quickly hit full capacity, Reynard said.
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Resort town sits in the heart of the Alps
In a region busy with tourists skiing on the slopes, authorities have called on the local population to show caution in the coming days to avoid any accidents that could require medical resources that are already overwhelmed.
Rescue efforts were ongoing and the area has been closed off with a no-fly zone in place over Crans-Montana, police said.
The Swiss blaze on New Year's Day comes 25 years after an inferno in the Dutch fishing town of Volendam on New Year's Eve, which killed 14 people and injured more than 200 as they celebrated in a cafe.
Swiss President Guy Parmelin said in a social media post that the government's "thoughts go to the victims, to the injured and their relatives, to whom it addresses its sincere condolences".
Thursday was Parmelin's first day in office as the seven members of Switzerland's government take turns holding the presidency for one year. Out of respect for the families of the victims, he delayed a traditional New Year's address to the nation meant to be broadcast on Thursday afternoon, Swiss broadcasters SRF and RTS reported.
Crans-Montana is in the heart of the Swiss Alps, just 40 kilometres north of the Matterhorn, one of the most famous Alpine peaks, and 130 kilometres south of Zurich.
Crans-Montana is one of Switzerland's most exclusive locales, famed for its year-round sunshine, which it owes to its position on a south-facing plateau in the Rhone Valley.
The ski resort is about two hours east of Geneva and visited by 3 million tourists each year, mainly from other parts of Switzerland, Italy and France.
The highest point of Crans-Montana, with a population of 10,000 residents, sits at an elevation of nearly 3000 metres, according to the municipality's website, which says officials are seeking to move away from a tourist culture and attract high-tech research and development.
With high-altitude ski runs rising about 3000 metres in the heart of the Valais region's snowy peaks and pine forests, Crans-Montana is one of the top venues on the World Cup circuit.
The resort will host the best men's and women's downhill racers, including Lindsey Vonn, for their final events before the Milan Cortina Olympics next month.
The town's Crans-sur-Sierre golf club stages the European Masters each August on a picturesque course.
The municipality was formed only nine years ago, on January 1, 2017, when multiple towns merged. It extends over 590 hectares from the Rhône Valley to the Plaine Morte glacier.
Tourists are drawn by its understated glamour, with high-end shopping and fine dining as well as extensive ski slopes and a lively apres-ski scene.
With a small population, the area is said to have a close-knit community as well as being a low-key place for celebrities to go skiing, golfing and dining.
– Reported with Associated Press and CNN
