The London Fire Brigade has confirmed that there have been fatalities in the Grenfell Tower fire, which consumed the block in west London in the early hours of the morning local time.
People have been desperately searching for their loved ones who live in the building as people appeared to be trapped inside, the Telegraph reports.
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.
Children are believed to be among those missing, as school students search for their friends.
There were reports that fire alarms in the main building did not go off, and residents were woken up and saved by neighbours banging on their doors, as well as screams of terror from others who lived in the building.
There were reports on social media of residents using bedsheets as makeshift ropes while others were reportedly seen jumping for their lives.
Ana Ospina said her 13-year-old niece Jessica was missing in the fire.
Jessica's other aunt, Sandra, wrote: "If anyone sees Jessica she should come to The Harrow Centre where the family are waiting for her. Or speak to any police officer to guide her".
She said Jessica may have been seen getting into an ambulance, and has been checking with local hospitals.
Ali Yawar Jafari
Hamid Ali Jafari said that he his 82 year-old father Ali Yawar Jafari had not been seem since the early hours of the morning as the family were trying to escape the blaze.
He said: "He was with my mother and sister in the lift and she said the lift stopped on the tenth floor and he said there was too much smoke and he couldn't breathe and he got out of the lift and then the doors shut and it didn't stop again till the ground floor."
Mr Jafari, who rushed to the scene from his home in Camden when he heard there was a fire, had tried to get in to find him but had been blocked by the emergency services. They had not be able to find him at any of the hospitals.
A mother of three trapped in the Grenfell Tower blaze rang a friend to tell her she feared she was about to die, it emerged on Wednesday.
The woman, named locally as Noora Jamal, called her friend at around 2am and said: "Forgive me, the fire is here, I'm dying."
Her daughter is understood to have escaped from the fire and is now being treated in hospital, but her two sons, aged 6 and 11, are both still missing.
Hibo Yussuf, 35, a friend of the missing woman, told The Telegraph: "We've heard that Nora's daughter is in hospital but hasn't been able to get hold of her mum. Noora called one of her friends to say 'Forgive me, the fire is here, I'm dying.'
"Now we don't know where she is or if she's dead or alive."
Mrs Yussuf said a teaching assistant from Avondale Primary School called Nadia was also missing, along with her husband and mother in law.
"They lived on the 22nd floor. I don't know what's happened to them. It's so horrible," she said.
Mr Power's sons told The Telegraph they are looking for their father.
He was on the 30th floor and is still missing.
Other missing people - and the terror residents faced
A woman named Suha told LBC that she had an elderly relative missing.
She said: "I can hear the screaming of people, I can hear them, and my neighbours all around got woken up by the screams.
"I have a relative who lives in the building, she lives on the 20th floor, and we don't know whether she is out or not. We have been here since it started."
Siar Naqshabandi, at the Rugby Portobello centre, told The Guardian he lives on the third floor and said his brother, who was in the building, heard no fire alarms. "I came back at about 1.45am and saw the building was on fire. I rang him [his brother] and said, get out."
He has more family living on the 23rd floor and an uncle is still missing. "They were telling people not to leave the building," he said. "I told them to get down. They said we're not allowed to get out."
Andy Manfrego, who lives yards away, was desperately searching for a relative trapped inside at 3am.
He told the Evening Standard: "It went up in seconds. It's been burning for nearly two hours and you can see people at the top still in there.
"Bits of the building keep dropping off it's awful. Everyone's waiting at the cordon trying to call their family members who could still be in there."
Ahmed Chellat told Good Morning Britain that he has five family members unaccounted for after they were told to stay inside their homes in the burning building.
He said: "When I saw the fire from my window, I rushed downstairs, I phoned my sister who lives in the same block, she was safe with her children.
"I phoned her and she spoke to me and said they were advised not to come out of the place and put white towels under the doors.
"Ten minutes later I phoned back and she said the smoke was getting into them very bad...and that was the last time I spoke to them".