A Japanese military helicopter has crashed in a built-up area of Kanzaki city in Saga, police told national broadcaster NHK, injuring two people on board the aircraft.

Video from the scene showed black smoke rising from a house not far from a nursery school, with emergency services tackling the fire.

The Boeing AH-64 combat helicopter ripped the top floor off the house and set it on fire, officials said.

The four residents of the damaged house were believed to have been away at the time of the accident, said Masaki Endo, a disaster official at the Saga prefectural government. No one else on the ground was believed to have been hurt, he added.

The helicopter belonged to the Ground Self-Defense Force's Metabaru training camp, defence ministry officials said. Both crewmembers who were on board at the time had suffered heart and lung failure.

Witnesses reported a big boom and ripping noises from the sky before the crash.

Defense Minister Itsunori Onodera said the helicopter fell nose down after losing contact with air traffic control. He said the cause of the accident is under investigation.

Prime Minister Shinzo Abe ordered the grounding of all 12 helicopters of the same type for safety checks, Kyodo News agency reported.

The crash follows a series of emergency landings and other incidents involving US military aircraft on Japan's southern island of Okinawa.