Volkswacht Bodensee - Apartment block in The Hague collapses after explosion

Four people have already been pulled out of the debris and taken to hospital, as elite teams with sniffer dogs deployed to rescue others trapped by the disaster.

It was not known how many people were still missing nor what caused the explosion in the block of flats not far from the centre of the city.

"We still don't know how many people might be under the rubble," a police officer on-site told AFP.

An AFP reporter on the scene saw dozens of fire trucks as firefighters battled the blaze from the ground and from higher positions. Police helicopters circled overhead.

Debris was strewn across the street and several windows had been blown out, the AFP reporter said.

Huge plumes of smoke were billowing from a large hole where the building stood, with an acrid smell in the air.

"I was asleep and suddenly there was this huge bang," Adam Muller, a 14-year-old local resident, told AFP.

"I looked out of the window and just saw flames. It's a massive shock," he added.

- 'Like an earthquake' -

Authorities warned locals to keep their windows shut and shut off ventilation systems due to the smoke.

Forensic investigators arrived on the scene to begin to probe a potential cause for the accident, an AFP reporter said.

Several homes appeared to have been destroyed by the fire, which broke out around 6:15 am (0515 GMT), according to the emergency services.

The three floors of the building consisted of shops on the ground floors and five two-storey apartments, authorities said, with living rooms on the second floor and bedrooms on the top.

The city's mayor Jan van Zanen travelled to the site to coordinate rescue efforts.

"It was like an earthquake," said a 53-year-old man who identified himself as Dimi, declining to give his family name.

"Something collapsed but we didn't see where it came from. I know these neighbours. My kids go to school with them."

"My new car has also been seriously damaged," he added.

Early images from public broadcaster NOS showed several dozen firefighters tackling a large blaze and breaking down doors to gain access to the block.

A picture from local news agency ANP showed one person being led away on a stretcher into a waiting ambulance.

Hospitals in the area were on standby to treat victims.

Residents told local media the apartment block was mainly inhabited by elderly people and families with children.

Around 40 residents of other blocks near the collapsed building have been evacuated. Some have been taken away by bus to an unknown location.

H.Kuenzler--VB