Flames tore up the 24-storey Grenfell Tower in north Kensington, leaving people trapped on upper floors, including children, some holding babies from windows and others jumping from their flats.
Commander Stuart Cundy, of the Metropolitan Police, said: “I can confirm six fatalities at this time but this figure is likely to rise during what will be a complex recovery operation over a number of days. Many others are receiving medical care.”
He said it was likely to be some time before police are able to identify the victims, adding that it was too early to speculate on the cause of the fire.
Residents who escaped the inferno complained there had been no fire alarm, with people relying on neighbours to wake them as the blaze spread.
They said official advice in the event of a fire had been to stay inside.
Mickey Paramasivan, who was in his seventh floor flat with his partner and child, said: ‘If we’d listened to them and stayed in the flat we’d have perished.’
London Fire Brigade said the cause of the fire was still being investigated.
But several residents reported one man had said it started in his faulty fridge.
Samira Lamrani, 38, said: ‘He was just beside himself.
‘He was just as surprised at how quickly the fire spread as anybody else.
‘I could hear him saying that he contacted the emergency services immediately and they reassured him everything would be under control within a short period of time, and obviously it wasn’t.’
Residents said refurbishment work had recently been carried out, with cladding on the outside of the structure and work on the gas supply.
A residents action group said its warnings about safety had fallen on ‘deaf ears’.
A blog post from the Grenfell Action Group in November 2016 said ‘only a catastrophic event’ would expose the concerns residents had.
The group said there was one entry and exit to Grenfell Tower during improvement works and it had issues with evacuation procedures.
Following the fire, the group posted: ‘All our warnings fell on deaf ears and we predicted that a catastrophe like this was inevitable and just a matter of time.’
London mayor Sadiq Khan said in a statement: ‘There will be a great many questions over the coming days as to the cause of this tragedy and I want to reassure Londoners that we will get all the answers.’
Pictures from the scene showed flames engulfing the block and a plume of smoke visible across the capital, while others showed residents looking out of windows in the block.
The leader of Kensington and Chelsea Borough Nick Paget-Brown said ‘several hundred’ people would have been in the block when the fire broke out.
Witnesses said the fire spread rapidly up the building, with some suggesting it was fuelled by gas.
Muna Ali, 45, said: ‘The flames, I have never seen anything like it, it just reminded me of 9/11.
‘The fire started on the upper floors ... oh my goodness, it spread so quickly, it had completely spread within half an hour.
‘My friends live on the fourth floor, someone knocked on their door, they didn’t know and they got out. They have three children.
‘Some people were knocking on doors but the people inside didn’t open the door.’
Ann Waters lives in a house at the foot of the tower and was forced to flee her home when burning debris began raining down.
The 57-year-old said: ‘It was the screaming that was the worst and I could hear that from the ground. All I could hear was ‘help, help, help’.’
She added: ‘It was like something out of a nightmare.’
Mr Paramasivan, who was woken by the smell of burning at around 1.30am, said: ‘I looked out into the corridor and saw there was smoke everywhere and neighbours running around and a fireman saying get down the stairs.
‘I went inside, grabbed my little girl and my girlfriend, and ran.
‘Our advice has always been if there is a fire stay in your flat, but if we had stayed in that flat we would have been perished. It just spread like wildfire, and the smoke alarm was useless, We would not have heard anything.
‘It was like something out of a disaster movie.’
He added: ‘I did see people working on a stairwell with a gas pipe over the past few weeks.
‘There was a lot of blue flames (in the fire) which made me think it was gas related and I think it was the plastic cladding that made it spread so fast.’
Actor and writer Tim Downie, who lives around 600 metres from the scene in Latimer Road, said: ‘It’s horrendous.
‘The whole building is engulfed in flames.
‘It’s gone. It’s just a matter of time before this building collapses.’
Jody Martin said he got to the scene just as the first fire engine was arriving.
He told the BBC: ‘I watched one person falling out, I watched another woman holding her baby out the window... hearing screams, I was yelling everyone to get down and they were saying ‘We can’t leave our apartments, the smoke is too bad on the corridors’.’
Fabio Bebber wrote on Twitter: ‘More screams for help as the fire spreads to another side of the building.
‘We can see how quick the fire spreads via the external panels. It’s unbearable hearing someone screaming for their lives at #grenfelltower.’
George Clarke, who presents the Channel 4 TV show Amazing Spaces, told Radio 5 Live: ‘I’m 100 metres away and I’m absolutely covered in ash.
‘It’s so heartbreaking. I’ve seen someone flashing their torches at the top level and they obviously can’t get out.’
Paul Littlejohn said: ‘Windows were smashing and exploding, people jumping out and trying to climb out with rope made of out of bed sheets.
‘It was a complete nightmare.
‘You’d think after millions of pounds was spent on the tower block that it would be safe and this event could not happen.’
London Ambulance Service said paramedics had taken more than 50 patients to five hospitals.
More than 200 firefighters were sent to tackle the blaze which was reported just before 1am on Wednesday.
Firefighters were on the scene within six minutes.
An acrid column of smoke could be seen rising from the building on Wednesday.
The charred structure still had pockets of flame rising from several storeys as desperate efforts to bring the blaze under control continued.
The Metropolitan Police have set up a casualty bureau for anyone concerned about their friends and family on 0800 0961 233.