Japan's new defence minister told the US military on Monday of his "many concerns" after it flew an Osprey tilt-rotor aircraft in the country following a weekend crash off Australia, the defence ministry said.
The Japan-based US Marine Corps MV-22 Osprey crashed on Saturday during an exercise off the Australian coast, leaving three service members missing.
An Australian naval ship has found the wreckage and drivers were preparing to try and locate the three, the defence ministry said Monday in Canberra.
Itsunori Onodera, appointed Thursday as Japan's defence minister, had asked the US to temporarily stop flying the aircraft in his country following the accident.
"We have still many concerns," Onodera said during a meeting with Major General Charles Chiarotti, deputy commander of US Forces in Japan, according to a defence ministry spokesman.
Japanese media said the flight took place on the southern island of Okinawa, where a squadron of Ospreys is stationed at the US Marines' Futenma base.
Chiarotti told Onodera the flight was necessary for operational reasons and that safety was confirmed, according to the ministry.
US Forces in Japan could not immediately be reached for comment.
The MV-22 -- 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.
The Okinawa-based aircraft which crashed was in Australia as part of a joint military exercise called Talisman Sabre, which has just ended in Queensland state.
There have been a series of deadly incidents, mostly in the United States, involving the aircraft.
In April 2000 19 Marines were killed in an MV-22 crash in Arizona.
Locals on Okinawa have protested at the deployment of Ospreys to Futenma, which sits in the middle of a crowded city.
In December a "controlled landing" of an Osprey just off the Okinawan coast during a training flight sparked local anger. The aircraft broke into pieces but no one was killed.