The fire began early Wednesday morning. Some 200 firefighters, backed up by 40 fire engines, have been fighting the blaze for hours. Photograph: (Reuters)
Police have said at least 12 people died in the fire that engulfed a 24-storey block of flats in west London.
The fire also injured at least 50 people, with some residents trapped asleep -- the fire began at about 1 am Wednesday morning -- inside the towering inferno.
The cause of the fire is still unknown.
Witnesses could hear screaming from the upper floors as the flames rose and one desperate resident could be seen waving a white cloth, news agency AFP reported.
Police and fire services attempted to evacuate the concrete block and said "a number of people are being treated for a range of injuries", including at least two for smoke inhalation.
"At this time I am very sad to confirm that there have been a number of fatalities, I cannot confirm the number at this time due to the size and complexity of this building," Dany Cotton, Commissioner of the London Fire Brigade told reporters.
"In my 29 years of being a firefighter, I have never ever seen anything of this scale," Cotton told reporters.
No less than two hundred firefighters with 40 fire engines are on the scene to combat the flames, Sky News reports.
At least 50 people are injured (WION)
The building is located in Lancaster West Estate, between Latimer Road Underground station and Westfield's White City shopping centre.
Police said: "At this stage we are aware of two people being treated at the scene for smoke inhalation."
It was earlier thought there were 27 storeys in the tower block, not 24.
"Fire is from 2nd to top floor of 27 storey building," the fire service had said on Twitter.
"Firefighters wearing breathing apparatus are working extremely hard in very difficult conditions to tackle this fire," London Fire Brigade assistant commissioner Dan Daly said.
"This is a large and very serious incident and we have deployed numerous resources and specialist appliances," he said.
London mayor Sadiq Khan tweeted: "Major incident declared at Grenfell Tower."
Actor and writer Tim Downie, who lives nearby, 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".
Police said in a statement they were called at 1:16 am (0016 GMT) "to reports of a large fire at a block of flats in the Lancaster West Estate".
The apartment block was built in 1974.
Local residents had warned a year ago about a potential fire risk caused by rubbish being allowed to accumulate during improvement works.
"This matter is of particular concern as there is only one entry and exit to Grenfell Tower during the improvement works," read a blog post by the Greenfell Action Group.
"The potential for a fire to break out in the communal area on the walkway does not bear thinking about as residents would be trapped in the building with no way out," it said.
Oh my. West London building is literally fully engulfed in fire. Terrifying scene. pic.twitter.com/rlUQQVHznb— Steve Kopack (@SteveKopack) June 14, 2017
London from my window right now. pic.twitter.com/DPMHGTPIdy— Jackson Harries (@JackHarries) June 14, 2017
(WION with inputs from agencies)