An action group at a west London tower block ravaged by fire have said their warnings fell on "deaf ears" after highlighting safety concerns about the block.

The cause of Wednesday’s blaze at the Grenfell tower, north Kensington, is not known, but a blog post from the Grenfell Action Group from November 2016 said “only a catastrophic event” would expose issues residents had.

Several hundred people would have been in the block when the fire was reported at 12.54am, while 30 have been taken to hospital.

The group said there was one entry and exit to Grenfell Tower during improvement works at the block in Latimer Road and it had issues with evacuation procedures at the building.

Following the fire, the group posted: “All our warnings fell on deaf ears and we predicted that a catastrophe like this was inevitable and just a matter of time.”

The group claimed access to the building was “severely restricted” for emergency services and other vehicles and that residents were advised to stay in their flats in case of fire.

The tower block was recently refurbished at a cost of STG8.7 million ($A14.7 million), with work completed in May last year.

The exterior of the 1970s-built tower was “modernised” with cladding and replacement windows, while additional homes were added using vacant space in the building, according to Rydon Construction.

On its website, Rydon Construction said: “Externally, rain screen cladding, curtain wall facade and replacement windows were fitted, improving thermal insulation and modernising the exterior of the building.”

But a resident of the 17th floor of the block, identified as Methrob, told LBC Radio that the “real issue was when it caught fire to the cladding outside”.

“That’s when I noticed the fire from outside when I looked out the window.

“By the time that we got downstairs, the fire had gone all the way up and it was just about reaching our windows on the 17th floor.

“The whole one side of the building was on fire. The cladding went up like a matchstick.”

Methrob said residents had been concerned about safety, adding there had been warnings “for over a year”.

London’s towering inferno, what we know


Reports of a fire at Grenfell Tower in North Kensington, west London, came in just before 1 am on Wednesday (1000 AEST).

The first fire crews arrived at the scene within minutes, and the London Fire Brigade soon declared it a major incident. The brigade sent 45 fire engines and over 200 firefighters to the scene.

Residents say the blaze appeared to start in an apartment on a lower floor and spread upward rapidly. The block was covered in thick black smoke and parts of it were still ablaze at midday Wednesday.

Police confirmed 12 people have died but they expect to toll to rise after a complex recovery operation that will last days.

Authorities say 65 people were rescued from the blaze. Ambulance officials say 78 people were being treated in hospitals across London for a range of injuries and smoke inhalation. Of those patients, 18 are in critical care.

Some witness reports say children and a baby were seen being thrown out of windows amid the blaze. It is not yet known how many people were in the building at the time and how many escaped.

The fire brigade says a structural engineer and expert crews believe the building is not in danger of collapsing.

Authorities say the cause of the fire is not yet known and declined to speculate about how it started and spread so quickly.

Grenfell Tower is a 24-story public housing block containing 120 homes that is part of the Lancaster West Estate. It was built in 1974 and owned by the local authority, the Royal Borough of Kensington and Chelsea.

The building was recently upgraded at a cost of STG8.6 million ($A14.4 million) , with work to modernise the exterior finishing in May 2016.

But residents said the fire alarm didn’t ring and that they had complained for years to local authorities about building safety in vain.

The Grenfell Action Group, a community organisation, says it has repeatedly warned about the risk of fire at the building since 2013. The group has raised concerns about testing and maintenance of firefighting equipment and about blocked emergency access to the site in recent years.