The aircraft, Sikorsky S-76 aircraft, belongs to a private firm Eczacibasi and crashed shortly after take off from the city’s Ataturk Airport.
Taxi driver Fikret Karatekin told broadcaster CNN Turk the helicopter struck the tower before crashing on a road.
“It hit the tower and crashed by spinning,” he said.
Another witness said: “I was driving. I heard an explosion… we saw pieces falling out of the sky.
“There was a lot of smoke. It exploded like a bomb. At first we thought it was a terror attack or something,”
Seven people were on board at the time – four Russians and three Turkish nationals including an executive of Eczacibasi and two pilots.