A Greek fighter jet has crashed into the Aegean Sea, leaving its pilot killed amid rising tensions with neighboring Turkey.
The single-seat aircraft crashed on Thursday north of the island of Skyros in the central Aegean, as it was preparing to land "after concluding an operational mission," according to the Greek air force.
Prime Minister Alexis Tsipras said the pilot died "in the line of duty" after returning from a patrol.
“A Greek pilot joins the pantheon of heroes. He fell in the defense of our national sovereignty and territorial integrity,” Defense Minister Panos Kammenos said in a message posted on Twitter with no mention of a possible cause of the crash.
Reports said the pilot may have blacked out during a combat exercise. The Greek armed forces announced a three-day period of mourning over the incident.
A Greek general staff source told AFP that the plane was returning from a mission to intercept Turkish fighter jets. "The mission was over and the plane was returning," the source said.
"We still don't know if there was an actual engagement with the Turkish air force," the officer added.
TV ERT, a state-run Greek-language TV channel run by Greece's national broadcaster Hellenic Broadcasting Corporation, cited military sources as saying that there had been no military engagement between Greek and Turkish forces.
In Turkey, state-run Anadolu news agency quoted Turkish security sources confirming that there were no Turkish air force jets in the area at the time of the incident.
Turkish and Greek warplanes regularly fly sorties in the area and occasionally engage in mock dogfights.
The crash comes at a period of heightened tensions between the two neighbors.
Earlier this week, Greek soldiers fired warning shots at a Turkish helicopter after it approached the small island of Ro, which is on the Greek side of the southeastern Aegean Sea.
Turkish President Recep Tayyip Erdogan and members of his government have been critical of Athens after its failure to extradite eight Turkish soldiers that Ankara said were part of an attempted 2016 coup.
In March, Turkey captured and is still holding two Greek soldiers who crossed the border, allegedly after being lost in the fog during patrol.
In 2006, a Greek pilot was killed when his plane collided with a Turkish jet during a mock dogfight in the Aegean.