The apartment block was built in 1974.
"In my 29 years of being a fire fighter, I have never ever seen anything of this scale", he said.
"Somebody did, a gentleman ran forward and managed to grab the baby". Others said they could see people inside using flashlights and mobile phones to try to signal for help from higher floors.
"We literally watched a man burn to death in his flat", she told CNN.
The blaze appears to be the worst since a 2009 fire in south London killed six people, including three children. "It's unbearable hearing someone screaming for their lives at #grenfelltower".
Pictures and videos from the scene show residents trapped inside their homes waving towels and flashing lights in a desperate bid for help.
"Thinking is really scary but the Grenfell Action Team believes that only a disastrous event will expose the incapacity and irresponsibility of the manager, KCTMO, and put an end to risky living conditions and neglect of health and safety regulations "By the building management organization, the document says".
Residents have been seen jumping from upper floors in scenes reminiscent of September 11.
Sadiq Khan, the city's mayor, said he was in close contact with the London Fire Commissioner and the heads of other emergency services.
He said: "It's horrendous". He said he heard sirens, helicopters and shouting and then saw the building engulfed in flames.
Ruks Maudu was in the building at the time of the fire with her grandson. "I wrapped the little one up because of the smoke and I just got them out".
"I always open my windows and I heard some unusual noises outside", she said.
"I got dressed, went downstairs and saw a neighbor".
There are 40 fire engines and 200 firefighters at the Lancaster West Estate, according to Daily Mail.
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London Ambulance Service says 50 people have been taken to five hospitals following a major fire in a high-rise residential building.
Cladding had been added to the outside of the building, blamed by some residents for helping the fire to spread so quickly.
"We can see how quick the fire spreads via the external panels".
George Clarke told Radio 5 Live that he was covered in ash even though he was 100 meters (yards) from the scene.
'I thought it might be a vehicle alarm outside and saw the glow through the windows.
He continued: "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".
While the firefighters have been making religious efforts to douse the fire that started 12 hours ago, some parts of the tower are still engulfed in fire.
Around 400 people are believed to have lived in the 120 flats in the Grenfell Tower, which caught fire in the early hours of today.
Former chancellor and now editor of the Evening Standard George Osborne tweeted: "Just seen this bad tower block fire near my home in W London. My prayers with those affected & heroes tackling it".
An action group at a west London tower block ravaged by a deadly fire has said its warnings fell on "deaf ears" after it highlighted safety concerns.
Residents at Grenfell Tower were reportedly told to "stay put" inside their flats in the event of a fire. He and his cousin have family living on the 18th floor of Grenfell and wanted to make sure they were OK.
London's Metropolitan Police, who also confirmed that there had been several fatalities, said that "a number of people" were being treated for a range of injuries and smoke inhalation and that "residents were continuing to be evacuated" from the tower. I woke up my auntie who was sleeping, it was about 1.15am, and we started to make our way down.
The leader of Kensington and Chelsea Borough council Nick Paget-Brown said "several hundred" people would have been in the block when the fire broke out.
Emergency services haven't been able to confirm exactly how many as yet.
"What a fire sprinkler does, is stop it immediately, you won't have a fire of an magnitude", Rowe said.
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