A fire at a hospital in southern Japan has killed 10 elderly people, prompting government demands for safety reviews across the country.

Police say eight others were injured in the blaze at the orthopaedic hospital in Fukuoka, that apparently started while patients were sleeping on Friday.

"We did our best in fire fighting to save lives, but it was a difficult situation," a fire station official told reporters.

"We received news of the fire at a very late stage, and there had been no attempt (by staff) to tackle the fire in its early stages," he said.

The fire raged for around two hours, having started at 2:20am local time (1720 GMT) at the four-storey building that was constructed in 1970.

All of those who died were between the ages of 70 and 89, including eight in-patients and two hospital workers, police said.

Local media reported the fire may have started at a treatment room, which had a laser device and thermal therapy equipment that used a water boiler.

Hours after the tragedy, Japan's fire and disaster management agency issued administrative guidance to fire headquarters nationwide that officials check hospitals to ensure medical organisations are prepared for nighttime fires.

It also sent seven officials to the scene to probe the cause of the disaster, an agency spokesman said.

While Fukuoka is a fairly modern city, in common with other parts of Japan many older neighbourhoods have narrow streets, which the local media said could have hampered access.