Four soldiers were killed on Monday after a Turkish military helicopter crashed in a residential area of Istanbul, the province's governor said.
"Unfortunately four of our soldiers became martyrs," Istanbul governor Ali Yerlikaya told reporters at the scene.
Yerlikaya said no other military personnel or civilian had been injured after the helicopter ploughed to the ground in the Cekmekoy district.
The incident happened around 1851 (1551 GMT), he said in televised comments.
Images on Turkish television earlier showed thick black smoke emanating from behind a white wall at the site on the Asian side of Istanbul.
Yerlikaya said the Istanbul public prosecutor had launched an investigation into the cause of the crash.
Four Turkish soldiers were killed last November after a military helicopter crashed in another residential area of Istanbul, hitting a four-storey building.
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