wo residents wait to be rescued as firefighters battle a huge fire raging through a multi-storeyed residential block in Valencia on Thursday. AFP

At least 10 people have died in a vast fire that ripped through a 14-storey apartment block in Valencia in eastern Spain, but officials warned on Friday that the death toll could rise sharply.

Nineteen people are still missing, a city hall source told AFP on condition of anonymity.

Experts said the building was covered with a highly-flammable cladding which could account for the rapid spread of the inferno, which began around 5:30 pm (1630 GMT) on Thursday.

Dramatic images showed the ferocious blaze throwing out clouds of black smoke as it consumed the highrise in the western Campanar neighbourhood.

"10 people have died," Jorge Suarez Torres, deputy director of emergency services for the Valencia region, told reporters, refusing to confirm the numbers of missing.

Fourteen people were treated for injuries of varying degrees, including a seven-year-old child and six firemen, and 12 of them were taken to hospital, according to emergency services.

Spanish media said the bodies were discovered with the help of drones, with Suarez Torres saying the firefighters had not yet managed to get into the building.

"We can't say when they will be able to get inside the structure," he said, indicating they were working on trying to cool the block, which witnesses said was quickly reduced to a skeleton.

 People react at the scene of a fire in an apartment building in Valencia on Thursday. Reuters

Spain's TVE public television said there were more than 130 flats in the building with 22 teams of firefighters called in to battle the blaze.

Esther Puchades, deputy head of Valencia's Industrial Engineers Association (COGITI), told local media that the fire had spread so rapidly because the building was covered with highly flammable polyurethane cladding.

Luis Ibanez, who lives nearby, told TVE he had looked out of a window and saw the flames engulfing the block "within a matter of minutes", saying it was "as if it was made of cork".

"I couldn't believe what I was seeing. The whole side of the building directly opposite was on fire, from the first floor to the sixth and seventh floor," he said.

"There was a really strong wind and the fire was spreading to the left at a huge speed."

'It's a disaster'

Neighbours gathered outside expressed shock at the scene and the thought of people being trapped inside.

"It makes your hair stand on end, the thought that people are inside and really suffering. It's a disaster because there could be people in there dying," Julia Pascual told AFPTV.

Footage on social media that was reposted by Spanish media outlets showed a father and daughter being rescued from a balcony where they were trapped.

"It's absolutely horrible, it gives you goosebumps to think about those people inside," said another local, Luis Alberto Clarin, who had just come home from work.

"It could have been me, it could have been my building."

Spanish Prime Minister Pedro Sanchez said he was "shocked by the terrible fire" and was in contact with the mayor and the region's leader "to offer whatever help needed" and extending his condolences to everyone affected by the blaze.

In October, a fire gutted a nightclub in the neighbouring region of Murcia, claiming 13 lives in what was Spain's deadliest nightclub fire in three decades.

Six people have been charged as part of a manslaughter probe and could face up to nine years behind bars if the deaths were found to be the result of negligence.

The fears of polyurethane cladding exacerbating the Valencia fire recalled the 2017 tragedy at London's Grenfell Tower.

In that incident, a fire at a 24-storeyed highrise in west London killed 72 people, with the blaze spreading rapidly due to the highly combustible cladding on the block's outside walls. A public inquiry into the disaster is still to publish its final report.

Agence France-Presse