A Greek navy helicopter crashed early on Thursday off the small island of Kinaros in the eastern Aegean Sea, killing a crew of three, a Greek Defence Ministry official said.
"The Agusta Bell helicopter was taking part in a military exercise. It had taken off from a frigate sailing in the area and disappeared from radar around 0045 GMT. Wreckage has been found near Kinaros," the official said.
Kinaros is an islet near the island of Amorgos.
The official said Turkey had issued a Notice to Airmen saying the Greek rescue operation was within its maritime search and rescue region and that all efforts should be coordinated with Turkish authorities.