Bryan Swenson was relieved of his duties last week "due to loss of trust and confidence in his ability to lead his command," III Marine Expeditionary Force told AFP in a statement.

Christopher Denver, executive officer for the Okinawa-based tilt rotor squadron, has been assigned as interim commanding officer, the statement said, without further details.

The sacking comes six months after US Marines were forced to mount a major search and rescue mission when an MV-22 Osprey crashed off the east coast of Australia.

Twenty-three of the crew of 26 were rescued but the search for the remaining three was eventually called off.

And in December, five crew members aboard a US Marine MV-22 Osprey were injured after what the Pentagon described as a "mishap" resulting in the plane landing in shallow water off Okinawa in southern Japan.

The MV-22 -- a hybrid helicopter-turboprop with a checkered 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.

However, residents in Okinawa -- which hosts the bulk of some 47,000 American troops in Japan under a decades-long security alliance -- have protested against the deployment of Ospreys in the country following the accidents.