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.

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.

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.