Reports say 30 people are in hospital and there are fears that more may be unaccounted for after a huge fire raged through the night at a west London tower block.
Firefighters are still tackling the blaze at Grenfell Tower in north Kensington, where hundreds of people are thought to live.
Eyewitnesses reported seeing people trapped inside their homes.
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.
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 of 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.'”
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 Fire Brigade assistant commissioner Dan Daly said firefighters were “working extremely hard in very difficult conditions to tackle this fire”.
“This is a large and very serious incident and we have deployed numerous resources and specialist appliances.”
London Ambulance Service medics specially trained in life-saving medical care in hazardous environments have also been sent to the fire.
The first reports of fire in the tower, in Latimer Road, on the Lancaster West Estate, came in at 00:54 BST.
The A40 Westway was closed in both directions. London Underground said the Hammersmith and City and Circle lines have been closed between Edgware Road and Hammersmith.
According to Kensington and Chelsea Council, the tower block contains 120 flats and is 24 storeys high.
It is managed by the Kensington and Chelsea Tenant Management Organisation (KCTMO) on behalf of the council and had undergone a two-year, £10m refurbishment that was completed last year.