This article contains details some readers may find distressing
Samuel Rapp, who was at a restaurant near Le Constellation bar in the Swiss ski resort of Crans-Montana when the fire broke out, described the scene as "horrible".
About 40 people were killed in the fire, police have confirmed, and 115 others injured - the majority seriously, suffering severe burns.
Mr Rapp said he was told of an "explosion" at the venue during the early hours of New Year's Day and went to investigate.
He told Sky News: "There were a lot of people at the entry trying to escape. And it was full and people [were] walking on everybody trying to escape.
"A lot of people were screaming trying to escape and I saw a lot of people on the floor."
Follow latest: Several dozen feared dead in fire
Mr Rapp said he witnessed someone place a jacket over a victim's face and saw "a lot of people" whose hair had been burned off.
He said: "Some people were without clothes."
Asked what kind of people were at Le Constellation, he said: "Everyone in the world comes here."
He said a lot of people come from England, from the Netherlands, and from around Switzerland.
Mr Rapp added: "The people were between 16 and 18. It's horrible."
Sky News' Home Editor Jason Farrell is at the scene and said those he has spoken to have been left traumatised by the tragedy.
"It's just an absolute shock," he said, as people were gathering by the cordon closing off the area around the bar.
"There's still some waking up to this, this is a real shock to the people of Crans-Montana."
Leon Christe, who works in Crans-Montana, told Sky News he was one of the first to the scene and tried to help as many people as possible by administering first aid.
He said: "It was very chaotic and very sad.
"Everywhere, there were young people who needed help, some had their clothes burned off.
"It was very traumatising."
Axel Clavier, a 16-year-old from Paris who survived the blaze, described "total chaos" inside the bar.
Speaking to The Associated Press, he said one of his friends had died and "two or three were missing".
The teenager didn't witness the fire start, but did see waitresses arrive with champagne bottles with sparklers.
Axel said he was suffocating and initially hid behind a table, then ran upstairs and tried to use a table to break a plexiglass window. It fell out of its casing, allowing him to escape.
He lost his jacket, shoes, phone and bank card while fleeing, but said: "I am still alive and it's just stuff."
"I'm still in shock," he added.
Authorities are yet to confirm the exact number of fatalities, although the Italian foreign ministry said Swiss authorities had reported at least 40 deaths to it.
The fire broke out at around 1.30am local time (12.30am UK time) on Thursday as people were celebrating the start of 2026.
A man speaking to BFMTV described people smashing windows to escape the blaze, some gravely injured.
Panicked parents also raced to the scene to see whether their children were trapped inside.
The man described seeing about 20 people scrambling to get out of the smoke and flames and compared what he saw to a horror movie as he watched from across the street.
The disaster occurred during the early hours of Thursday at Le Constellation, a bar in the Alpine ski resort of Crans-Montana.
Swiss President Guy Parmelin has described the fire as "one of the worst tragedies our country has ever experienced."
Here is what we know so far.
Follow latest: 'Around 40 people' killed in Swiss ski resort fire
How many people have died or been injured?
Swiss police broke the news on Thursday afternoon that about 40 people had been killed in the blaze.
But they have not yet confirmed the exact number, with services still reeling from the accident and the identification of badly-burned victims ongoing.
In a news conference, police said about a further 115 had been wounded, the majority seriously.
Many of the victims were young people.
The evening "should have been a moment of celebration and coming together, but it turned into a nightmare," said Mathias Renard, head of the regional government.
The intensive care unit of the local hospital is full, Mr Renard said earlier. Patients were being transferred to other facilities around the country.
In total 13 helicopters, 42 ambulances, 150 paramedics and 70 firefighters were mobilised to the blaze.
Leon Christe, who works in Crans-Montana, told Sky News he was one of the first to the scene and tried to help as many people as possible by administering first aid.
He said: "It was very chaotic and very sad. Everywhere, there were young people who needed help, some had their clothes burned off.
"It was very traumatising."
Where did the incident happen?
The bar is in Crans-Montana, in the Valais region at the heart of the Swiss Alps, which is popular with tourists from Britain and across Europe.
It is 40km (25m) north of the Matterhorn, one of the most famous Alpine peaks, and approximately two hours from the Swiss capital of Bern.
Swiss President Guy Parmelin said the tragic incident "took place in a place that is dedicated to life and joy... what an incredible and dreadful contrast."
What happened?
The incident occurred at roughly 1.30am local time (12.30am UK time) while guests were celebrating the start of 2026.
Seconds after noticing the smoke, a witness contacted police, and the first officers had arrived by 1.32am, Valais Canton police commander Frederic Gisler said during the Thursday afternoon news conference.
The cause is not officially known, but two theories have emerged, and officials have ruled out any sort of attack. There are no suspects and no one has been arrested, as of Thursday afternoon.
Italy's ambassador to Switzerland, Gian Lorenzo Cornado, at the scene, told Italy's Sky TG24 that the blaze may have been started by someone letting off a firecracker inside the bar.
However, two French women who claim to have escaped from the venue after the fire broke out told BFMTV that the blaze originated from one of the "birthday candles" placed on champagne bottles.
"One of them was brought too close to the ceiling, which caught fire. In a few dozen seconds, the whole ceiling was on fire. Everything was made of wood," one of the women said.
During the news briefing, officials were asked whether bottles containing sparklers were used in the bar.
Valais Canton attorney general Beatrice Pilloud replied that only a few hours had passed, and she was not in a position to confirm.
What are the nationalities of the victims?
Authorities have warned it may take "several days" to identify the dead.
Victims are expected to be of various nationalities, Valais Canton police commander Frederic Gisler said.
"Because it is an international resort, we think that there are international victims," he added.
On Thursday morning the Italian foreign ministry said many victims had not yet been identified due to the severe burns on their bodies.
Among the injured were two French and a dozen Italian citizens.
About another 16 Italians have been reported missing, with around a dozen more being treated in hospital, Italian foreign minister Antonio Tajani said earlier.
The UK embassy in Switzerland said late morning it had "not been approached for assistance" but would "continue to monitor the situation".
Yellow alerts are in place in other areas, as people face a wintry start to 2026.
Amber warnings for heavy snow showers in parts of Scotland have been issued by the Met Office.
They are in place from midday on Friday to midday on Saturday.
Snow could bring disruption to parts of northern Scotland. The areas covered in the amber warnings include Angus, Perth and Kinross, Aberdeen, Aberdeenshire, Moray, and the Highlands.
Around 10-20cm of snow is likely at low levels, with 30-40cm possible on high ground, while winds could lead to temporary blizzard conditions, according to the Met Office.
It added that some delays and cancellations to rail and air travel are likely, as are power cuts and disruption on the roads, while some rural communities may be cut off.
Meanwhile, there is a yellow warning for snow and ice on Friday across large parts of England and Wales, including Chester and Greater Manchester down to London and Kent.
The warning lasts from midnight to noon.
Snow up to 5cm could cover some areas, especially on higher ground in parts of North Wales and northwest England.
Separate yellow warnings are in place for Northern Ireland between midnight and 10am on Friday.
Weather warnings are already in force on Thursday in Scotland, with a yellow warning of snow and ice covering the northern part of the nation.
The Met Office has said there could be 2-5cm by the evening, with 10cm accumulating by Friday morning, while up to 20cm could build up above 200 metres.
The warning is in force until midnight on Friday and at the weekend it extends further south, covering the area down to Perth and southerly parts of Argyll and Bute until midnight on Sunday.
Read more:
What we know about Swiss ski resort fire
Maresca leaves position as Chelsea head coach
Meanwhile, the UK Health Security Agency (UKHSA) has issued health warnings for the start of the year.
It previously issued amber cold health alerts in the North East and North West of England.
However, yellow alerts have been upgraded to amber across the East Midlands, West Midlands, South East, South West, East of England, Yorkshire and the Humber, and London.
These warnings are in place until 10am on 6 January.
The UKHSA said it means the weather is "likely" to cause significant impacts across health and social care services, including a "rise in deaths" among those with health conditions or aged 65 or over.
In a statement shared by Gloucestershire Constabulary, Tom Shearman said: "I have stared at my keypad for what seems like an eternity waiting for the words to appear.
"I have no way to thank any of you for the unbelievable out of this world generosity that you have shown to me in the darkest of hours.
"My life, the lives of my loved ones, my friends and the whole community changed on Boxing Day. Most importantly, and tragically, three of the greatest humans to ever grace our presence were taken from not just me, but all of us.
"I cannot begin to describe the anguish and trauma of the events of Boxing Day 2025. My family had its very core, its very essence, ripped from it in the most violent way."
The bodies of Fionnghuala Shearman, known as Nu, and their children, Eve and Ohner, were found in the property in Stroud. Their pet dog, Hutch, also died in the fire.
Mr Shearman was taken to hospital for treatment, but has since been discharged. He attempted to rescue his family but was beaten back by the severity of the blaze.
Emergency services were called to the family's mid-terrace Cotswold stone cottage on Brimscombe Hill at about 3am on Boxing Day.
Mr and Mrs Shearman, who ran a bespoke handbag manufacturer, had been awoken by the fire and tried to reach their children in the rear bedroom.
Police believe the fire started on the ground floor and investigations are ongoing to establish the cause, but it is not being treated as suspicious, rather as a "tragic accident".
The fire destroyed the roof, the ceilings and stairs, as well as causing other significant internal damage.
Deputy chief fire officer Nathaniel Hooton said firefighters worked extremely hard to get in to the house as the fire raged.
An online fundraising appeal launched for Mr Shearman has so far raised more than £300,000.
Mr Shearman's statement continued: "My family and friends have rallied around and provided me with more than the bare essentials. I have a roof (and many offers) over my head, clothes on my back, food - most importantly company and compassion. I will heal.
"I have already started the ball rolling on a plan that came to me just as I was falling past the precipice of the abyss. I will make sure my unbelievably talented, empathetic, compassionate and beautiful wife's legacy of craft, design and making lives on," he said.
"As will I ensure that my bright spark Eve's legacy of enjoyment from books and writing be carried on. Along with my incredible son's sheer compassion and desire to help people."
"Please all take every opportunity to hug your loved ones, tell them you love them. Because, as Paulo Coelho said, one day you will wake up and there won't be any more time to do the things you want. Do it now."
The bloody violence marks a significant escalation of the protests over Iran's ailing economy, after authorities on Tuesday unusually offered to set up a "dialogue mechanism".
A "source with knowledge" cited by the semi-official Fars news agency said clashes in the western city of Lordegan between police and what it said were armed protesters had killed multiple people.
According to the rights group Hengaw, security forces opened fire on the protesters in Lordegan, killing and wounding several in the crowd.
Meanwhile, authorities confirmed one death in the western city of Kuhdasht, and Hengaw said another had been shot dead in the central province of Isfahan.
The unrest over soaring inflation and a record slump in the currency began on Sunday among shopkeepers and traders in the capital Tehran.
But they have since spread to different groups and parts of the country, with university students in Tehran joining in, and demonstrators attempting to break into a government building on Wednesday.
Some protesters were detained yesterday in the western provinces of Kermanshah, Khuzestan and Hamedan, according to Hengaw.
The Revolutionary Guards - a military force that reports directly to Supreme Leader Ali Khamenei - said a member of its Basij volunteer paramilitary unit had been killed in Kuhdasht, and 13 others wounded.
This week's demonstrations are the first since the country was pounded by airstrikes in the summer, which prompted a momentary wave of patriotism and solidarity.
But this week frustrations boiled over, as the economy suffers from Western sanctions, 40% inflation and the fallout from Israeli and US attacks on the country's nuclear infrastructure and military leadership.
It is a dangerous and testing moment for Iran's authorities, with limited options at their disposal to alleviate the problems.
👉Listen to The World with Richard Engel and Yalda Hakim on your podcast app👈
They are often heavy-handed in their response to protests.
But this week they appeared to offer an unusually conciliatory gesture to open a dialogue with protesters, alongside their security response, which could yet escalate.
On Thursday government spokesperson Fatemeh Mohajerani reiterated that officials would speak directly to representatives of trades unions and vendors, though details remain unclear.
The activist news site HRANA reported a heavy presence of security forces across cities on Wednesday, with arrests, shootings and clashes in some areas.
State media said students had been detained and then released during the demonstrations.