Okinawa Governor Tamaki Denny has expressed serious concern over the use of Osprey tilt-rotor transport aircraft following a failed takeoff in his southern Japanese prefecture. He called the incident "extremely regrettable."

An Osprey of Japan's Ground Self-Defense Force suffered partial damage when it lost balance while attempting to take off from the country's westernmost island of Yonaguni on Sunday.

The aircraft was on a joint field training exercise with US forces that began on Wednesday.

Tamaki told reporters on Monday that the incident occurred even though the prefecture had asked the authorities to refrain from flying the US-made tilt-rotor aircraft.

He said he wonders what Japan's Defense Ministry thinks of using the Osprey in Okinawa despite the local opposition to the aircraft's deployment. He said he will ask for the ministry's view after the ongoing training ends.

Tamaki added that he is seriously worried that the Osprey's operations could be close to a perilous situation and they may have become an everyday event.

He also took issue with the transparency regarding the operations. He said another serious question is how the ministry is giving detailed explanations of the matter based on facts.

The governor expressed his intention to carefully monitor the Japan-US joint training, and file a request if necessary.