The Bell UH-1 helicopter crashed onto a street between apartments in the Asian district of Sancaktepe, where a military base is situated, after colliding with the roof a building.
"A military helicopter crashed in Samandıra district while performing a training flight. Four soldiers were killed and another was injured," Istanbul Governor Ali Yerlikaya said.
Media reports said the helicopter crashed due to a technical fault prior to landing.
Rescue and emergency teams were dispatched to the crash site immediately.