A US Osprey military aircraft with eight crew on board crashed on Wednesday off the coast of Japan, the coastguard said.
"We received information at 2:47 pm (0547 GMT) today that the US military's Osprey crashed off Yakushima Island," a spokeswoman told AFP.
"We were also notified that there were eight crew members on board," she added. "There is no further information at the moment."
The island of Yakushima lies south of Japan's southernmost main island Kyushu.
Japanese broadcaster NHK reported that the Osprey departed from the Iwakuni US base in the Yamaguchi region headed for the Kadena base in Okinawa.
NHK also cited defence ministry sources as saying that the aircraft was a CV-22 Osprey belonging to the US Yokota air base in Tokyo.
The tilt-rotor Osprey aircraft has a troubled history, with a string of fatal crashes over the years.
In August, a crash in northern Australia killed three US marines among the 23 on board.
The Boeing MV-22B Osprey crashed on Melville Island, north of Darwin during a military exercise for locally based troops.
Eight other US Marines needed hospital treatment including one of them in intensive care.
Four US Marines were killed in Norway last year when their MV-22B Osprey aircraft went down during NATO training exercises.
Three Marines were killed in 2017 when an Osprey crashed after clipping the back of a transport ship while trying to land at sea off Australia's north coast.
And 19 Marines died in 2000 when their Osprey crashed during drills in Arizona.
This month five US service members were killed when a helicopter crashed into the Mediterranean during a training exercise.
Officials did not specify where the aircraft was flying from, but the United States has deployed a carrier strike group to the Mediterranean as part of efforts to prevent the Israel-Hamas war from spiraling into a regional conflict.
There have been multiple other crashes of US military aircraft in recent years, including an F-35 stealth warplane that went down in South Carolina in September, with the pilot able to eject.
In April, three US soldiers were killed and another injured when two helicopters returning from a training mission in a remote area of Alaska collided.
The previous month, two US Army helicopters crashed during a nighttime training mission in Kentucky, killing all nine soldiers on board.
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