A fire has killed at least 26 people at a drug abuse treatment centre in Baku, the capital of Azerbaijan.

Four others were rescued from the blaze and taken to hospital, reported the country's APA news agency.

Footage on Azeri news channel Sahar TV showed firefighters battling intense flames as they billowed out of a single-storey building with bars over the windows.

The fire tore through a part of the clinic where inpatients sleep, reported the station.

A health ministry source told Reuters that 26 people were confirmed to have died, although local media reported the death toll as 30.

The fire broke out early on Friday morning at the Republican Narcological Dispensary in the city's Khatai district.

Fire crews reportedly had the flames under control by 8.20am local time (4.20am GMT.)