The US Marine Corps (USMC) has reportedly grounded its fleet of MV-22 Osprey aircraft in Japan, following a crash involving the tiltrotor military aircraft.

Tokyo has asked the US military to suspend Osprey flights after one such aircraft crash landed in the south-west of Okinawa island, Reuters reported.

On 12 December, an MV-22 Osprey with Marine Aircraft Group 36, 1st Marine Aircraft Wing crashed into the sea while conducting a landing in shallow water off the Okinawa coastline of Camp Schwab, leaving five crew members injured. The accident is the first Osprey crash in the country.

"We regret the accident, but we do not regret the work of our young pilots."

All five crewmembers were airlifted via HH-60G by the 33rd Rescue Squadron from Kadena Air Base to the US Naval Hospital aboard Camp Foster for treatment.

A formal investigation has been launched into the incident.

Japan Defence Minister Tomomi Inada was quoted by The Guardian as saying: “It is deplorable that the accident occurred at a time when people in Okinawa and other areas in Japan are taking a considerable interest in the safety of the Osprey.”

The US military believes that the crash occurred due to an oil duct problem during the aircraft’s refuelling, the newspaper reported.

USMC commander lieutenant general Lawrence D Nicholson was quoted by NHK as saying: "We regret the accident, but we do not regret the work of our young pilots.”

The US said that it has two Osprey squadrons in Japan. However, it did not reveal the exact number of aircraft. Japan's ground self-defence forces is planning to commission 17 Ospreys, starting in April 2019.

Built by Bell Helicopter and Boeing Rotorcraft Systems, the V-22 Osprey employs tiltrotor technology and it can take off, land and hover like a helicopter.