At least 12 people have been killed after a huge fire engulfed and destroyed a large block of London flats - and the death toll is expected to rise.

The Metropolitan Police said people may still be missing inside Grenfell Tower after the night-time inferno ripped through more than half of the 24-storey building.

A "complex and lengthy" recovery operation remains ongoing at the 1970s tower near White City in west London, which was recently refurbished at a cost of £8.7 million.

More than 70 people have been treated across six hospitals, 18 of whom are in critical care, but the London Fire Brigade (LFB) said it had "absolutely no idea" how many individuals remain unaccounted for.

Forty fire trucks supported by 250 firefighters responded to the blaze, which began shortly before 1am.

London Fire Brigade said the blaze was "unprecedented in terms of scale, speed and spread" as crews continued to tackle it on Wednesday evening.

Director of safety and assurance Steve Apter said firefighters "have been able to search almost all the building now" and said his crews "intend to be here through the night".

Witnesses saw people trapped inside their homes, screaming for help and jumping from windows, while desperate women threw their children to safety.

One witness saw a resident throw a baby from "the ninth or 10th floor" into the arms of a member of the public below.

Prime Minister Theresa May, who held a cross-Government meeting to coordinate a response, described the fire as "tragic".

"The Prime Minister is deeply saddened by the tragic loss of life in the Grenfell Tower and is being kept constantly updated on the situation," a spokesman said.

Policing and Fire Minister Nick Hurd later confirmed emergency checks are to be carried out on tower blocks going through similar refurbishment.

The cause of the blaze is currently unknown, though reports suggested a "faulty fridge" may have sparked the blaze.

London Fire Brigade Commissioner Dany Cotton said crews were likely to remain at the scene for at least 24 hours and said firefighters had rescued a "large number" of people from the building.

She confirmed crews had only managed to reach the 19th or 20th floors of the 24-storey block, as London Mayor Sadiq Khan said questions need to be answered over why they couldn't reach the top.

What we know at a glance:

Video footage showed flames from near the bottom to the top of the building.

Actor and writer Tim Downie, a nearby resident, described the block as looking close to collapse.

Local resident, Joanna O'Connor, said she awoke to screams and sirens.

"At about 2am (I was) woken up by screaming, sirens and helicopters. We came outside and were confronted with the building that was completely engulfed in flames," she said.

"It was a real shock and there were hundreds of people lining the streets, we could still hear screaming from the building and people were milling around in shock crying."

Local Omar Salha described hearing "children screaming for help" on Twitter.

Eyewitness Tia Abrhams told Good Morning Britain: "It was horrible. There were people banging on their windows, screaming for help.

"There was even two young children literally staring down towards everyone at the bottom.

"You could hear people screaming in pain from the fire."

Ahmed Chellat said he had family inside the building, but did not know whether they were trapped inside.

Mr Chellat said he spoke to his brother-in-law, who has a wife and three children living on the 21st floor, who were told to remain inside the block by emergency services - but they have not been heard from since.

Twitter user Omar Salha described hearing "children screaming for help".

Eyewitness Tia Abrhams told Good Morning Britain: "It was horrible. There were people banging on their windows, screaming for help.

"There was even two young children literally staring down towards everyone at the bottom.

"You could hear people screaming in pain from the fire."

Ahmed Chellat said he had family inside the building, but did not know whether they were trapped inside.

Mr Chellat said he spoke to his brother-in-law, who has a wife and three children living on the 21st floor, who were told to remain inside the block by emergency services - but they have not been heard from since.

Actor Mr Downie 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. I just hope they have got everyone out."

Aerial footage showed the extent of the fire, with huge flames and plumes of smoke rising into the air.

One resident said he only discovered the fire when he heard people screaming from outside his window.

And he claimed the fire alarm was barely audible, comparing it to the noise a lift door makes.

Another Grenfell resident told ITV News that no fire alarm had gone off on the 16th floor.

Concerns about fire safety at Grenfell Tower had reportedly been raised months ahead of the blaze.

Mr Chellat claimed residents had long warned of a fire risk at the block.

"We have raised concern of the safety for quite some time," he told GMB.

"I'm not an expert, but I think it's the plastic they put on the outside [that] really triggered the fire badly."

Labour leader Jeremy Corbyn said he feared spending cuts may have compromised the fire safety response and confirmed he would seek answers from Thursday once all efforts were made to save lives.

He referred to comments from Labour MP Harriet Harman, who he quoted as saying: "If you cut local authority expenditure then the price is paid somewhere."

Ms Harman drew links between the fire and warnings that were raised as a result of a deadly blaze in her constituency of Camberwell and Peckham in 2009.

Policing and Fire Minister Nick Hurd said the government wanted to provide reassurance to people living in similar blocks as soon as possible.

"We have discussed with the Department for Communities and Local Government, local authorities and the fire service a process whereby we seek to identify towers that might have a similar process of refurbishment, run a system of checks so that we can, as quickly as possible, give reassurance to people," he said.

According to Kensington and Chelsea Borough council leader Nick Paget-Brown "several hundred" people would have been in the block when the fire broke out.

The 1970s tower block was recently refurbished for some £8.7 million, with work completed in May 2016.

Its exterior was "modernised" with cladding and replacement windows, while additional homes were added using vacant space in the building.

Construction firm Rydon, which completed the refurbishment, said it was "shocked" to hear about the "devastating fire".

In a statement, the company said it had met all required building control, fire regulation and health and safety standards.

Meanwhile, London Mayor Sadiq Khan urged people to follow the London Fire Brigade's Twitter feed for updates.

The Met has set up a casualty bureau for anyone concerned about friends and family, which people can contact on 0800 0961 233.