Okinawa Prefecture in southwestern Japan has again asked for a suspension of flights by US Osprey military aircraft.

A CV-22 Osprey of the US Air Force crashed on Wednesday into the sea off an island in Kagoshima Prefecture.

On that day, the Okinawa government filed a request with Japan's authorities of the Defense and Foreign ministries for a suspension of US Osprey flights until the cause is determined.

But some Ospreys operated by the US Marine Corps have been flying from the US Futenma Air Station in the prefecture. The Marines use MV-22 model Ospreys.

The Okinawa government on Friday made a renewed request to the ministries' offices in the prefecture. It said US Ospreys must not fly even in search and rescue operations, and called for using other types of aircraft instead.

Okinawa Governor Tamaki Denny said in a statement on Thursday that it is very regrettable Osprey flights have been confirmed in the prefecture after the crash. He added that he has serious doubts about the use of the Osprey, even in search and rescue operations.

Meanwhile, Kanagawa Prefecture, west of Tokyo, and its municipalities that host US military facilities, also asked the central government to urge the military to suspend Osprey flights.

They called for finding the cause of the crash, taking preventive measures and grounding the aircraft until safety is confirmed.