Several people have died after a huge fire raged through the night at a west London tower block, a fire chief says.
Firefighters are still tackling the blaze at Grenfell Tower in north Kensington, where eyewitnesses said people were trapped inside, screaming for help.
More than 50 people are being treated in hospital, says London Ambulance.
The BBC’s Andy Moore said the whole 24-storey block had been alight and there were fears the building might collapse.
Eyewitnesses said they saw lights – thought to be mobile phones or torches – flashing at the top of the block of flats, and trapped residents coming to their windows – some holding children from windows.
The Met Police has set up an emergency number on 0800 0961 233 for anyone concerned about friends or family.
London Fire Commissioner Dany Cotton said there had been “a number of fatalities” but she could not say how many because of the “size and complexity” of the building.
“This is an unprecedented incident,” she told reporters.”In my 29 years of being a firefighter, I have never ever seen anything of this scale.”
She said the cause was not yet known.
Paul Munakr, who lives on the seventh floor, managed to escape.
“As I was going down the stairs, there were firefighters, truly amazing firefighters that were actually going upstairs, to the fire, trying to get as many people out the building as possible,” he told the BBC.
He said he was alerted to the fire not by fire alarms but by people on the street below, shouting “don’t jump, don’t jump”.
“Now, honestly I don’t know for certain if people jumped off the building to get away from the fire, but the main thing for me with this incident is the fact that the fire alarms didn’t go off in the building,” he said.
Eyewitness Jody Martin said: “I watched one person falling out, I watched another woman holding her baby out the window… hearing screams.
“I was yelling at everyone to get down and they were saying ‘We can’t leave our apartments, the smoke is too bad on the corridors.'”
Michael Paramaseevan, who lives on the seventh floor with his girlfriend and young daughter, said he ignored official advice to stay in your home.
“If we had stayed in that flat, we would’ve perished. My gut instinct told me just to get the girls out. I wrapped the little one up because of the smoke and I just got them out.”
The BBC’s Andy Moore said: “We’ve seen debris falling from the building, we’ve heard explosions, we’ve heard the sound of glass breaking.
“The police keep pushing back their cordons, pushing back members of the public for fear the building might collapse.”
London Mayor Sadiq Khan said a “major incident” had been declared.
“Several hundred” people would have been in the block when the fire broke out, leader of Kensington and Chelsea Borough Nick Paget-Brown said.
The first reports of fire in the tower, in Latimer Road, on the Lancaster West Estate, came in at 00:54 BST. Three hours later, people were still being evacuated from the tower, the police said.
Grenfell Tower was built in 1974 by Kensington and Chelsea Borough Council. It’s part of the Lancaster West Estate, a sprawling inner-city social housing complex of nearly 1,000 homes.
Grenfell Tower underwent a two-year £10m refurbishment as part of a wider transformation of the estate, that was completed last year. Work included new exterior cladding and a communal heating system.
The 24-storey tower, containing 120 flats, is managed by the Kensington and Chelsea Tenant Management Organisation (KCTMO) on behalf of the council.
The local Grenfell Action Group had claimed, before and during the refurbishment, the block constituted a fire risk and residents had warned that access to the site for emergency vehicles was “severely restricted”.