Japanese Prime Minister Shinzo Abe on Wednesday regretted the crash-landing of a US Marine aircraft in its waters.

The US Marine Corps MV-22 Osprey aircraft crash landed in the sea off Okinawa Prefecture, south of Japan, on Tuesday night, Efe news reported.

“It is regrettable that an accident of this seriousness occurred. It is essential that security be guaranteed. We have called on the US to disclose the cause and guarantee the safety of its flights,” Abe told reporters.

The Pentagon confirmed that two of the five crew members in the US Osprey that “landed in shallow water” one km off the coast, were injured.

Japan’s Defence Minister Tomomi Inada called on the US military authorities to ground its Osprey aircraft flights until the cause of the accident was known and safety was assured.

These aircrafts are capable of vertical takeoffs and landings.

The US Defence Department Spokesman Jeff Davis said that Washington “will absolutely get to the bottom of the cause” of the accident and promised to “learn from it so that it doesn’t happen again.”

Japan decided in 2012 to allow the operations of the controversial US military Osprey aircraft, whose security was under cloud due to several accidents.