One of the two MV-22 Ospreys landed at Amami Airport in southwestern Kagoshima prefecture Tuesday afternoon, according to the Kyodo and Jiji news agencies.

The tilt-rotor aircraft left the Japanese airport two hours later, interrupting some commercial flights, public broadcaster NHK said.

The other Osprey made an emergency landing further south at the US Kadena Air Base in Okinawa Friday afternoon, Kyodo said, quoting government sources.

There were no reports of injuries or damage following the two incidents.

Immediate confirmation of the news reports was not available.

The Osprey, a hybrid helicopter-turboprop with a chequered safety record, has two engines positioned on fixed wingtips that allow it to land and take off vertically. It can travel much faster than a helicopter.

Several accidents involving US military aircraft in Japan have stoked tensions between Washington and Tokyo and led to protests against the deployment of Ospreys by residents living near US bases.

The incidents have included emergency landings by US military helicopters, a piece of a helicopter falling on the grounds of a Japanese school, and the deadly crash last year of an MV-22 Osprey which forced a massive rescue operation.

US Defense Secretary James Mattis apologised to his Japanese counterpart over the mishaps in January.