A fire has broken out at a hospital in southern Japan, killing 10 people.

Another eight people were injured in the fire, which started on the ground floor of the four-storey orthopedic hospital while patients were sleeping.

Fukuoka police said eight of the dead were patients, and the remaining two were hospital staff.

Several of those injured were in serious condition. Akiharu Otsu, a Fukuoka city fire department official, told journalists the fire had been extinguished only after burning down most of the building.

There was no sign of an initial fire extinguishing effort at the hospital and fire-proof doors on the second and third floors were not properly used, an unidentified fire department official said in a televised news conference on NHK public television. The cause of the blaze is under investigation.