A massive fire engulfed a 24-storey housing block in central London in the early hours before dawn on Wednesday, leaving at least six people dead and injuring 74 others.
The number is expected to rise, police say, as the inferno seems to have trapped residents as they slept.
"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," police commander Stuart Cundy said in a statement.
London's Ambulance Service said 74 people are being treated following the massive apartment blaze in west London.
The fire that started just before 1 am, spread across the high-rise Grenfell Tower block of apartments in the north Kensington area like wild fire, witnesses said.
Black smoke billowed high into the air for hours after the blaze broke out.
Residents rushed to escape through smoke-filled corridors after being woken up by the smell of burning. There were reports that some residents leapt out of windows to escape the flames.
London Fire Brigade said the fire engulfed all floors from the second to the top of the 24-storey block.
More than 200 firefighters using 40 fire engines fought for hours to try to bring the blaze, one of the biggest seen in central London in memory, under control.
More than 12 hours after the fire broke out, the building was still smouldering, though the building was not in danger of collapse.
Firefighters rescued large numbers of people - some of them in their pyjamas - from the 43-year-old block, a low rent housing estate which overlooks up-scale parts of the Kensington area.
By mid-day, police said six people had been killed and they cautioned the death toll was likely to rise.
Fire-fighters still had to reach the top four floors of the building where several hundred people live in 130 apartments.
The cause of the fire, which left the tower block a charred, smoking shell, was not immediately known.
The block had recently undergone major repairs of the exterior, which included new external cladding and replacement windows.
London mayor Sadiq Khan said the fire raised questions over safety of high-rise blocks like Grenfell Tower.
The local council of Kensington and Chelsea, which owns the block, said it was focusing on supporting the rescue and relief operation. It said the causes of the fire would be fully investigated.