Belonging to the Eczacibasi group of companies, it had been carrying a Turkish official, the firm's four Russian guests and two Turkish pilots.
Initial reports said the helicopter crashed into a television tower.
The helicopter is reported to be a privately-owned Sikorsky S-76 that crashed after taking off from Istanbul's Ataturk Airport.
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Authorities initially recovered five bodies from the crash site, but Mayor Kadir Topbas later said that all seven on board were killed.
Images posted on social media showed huge plumes of black smoke billowing from the crash scene in Buyukcekmece district.
"It hit the tower and crashed by spinning", taxi driver Fikret Karatekin told CNN Turk.
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But one passenger, who was sat across the aisle from the man, was told by staff the man had threatened the pilot. Speaking with CBS Los Angeles , traveller Eileen Berstrom said the incident was "ridiculous".
The cause of the crash was under investigation, he said.
The information was confirmed by Eczacibasi chairman Bulent Eczabicasi, who stated the Russians were on a business trip to visit a company factory in the town of Bozuyuk.
The tower, which is no longer used for transmitting television signals, has a restaurant at the top it.
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"The head of our company in Russian Federation, and also four our clients from Russian Federation - the guests who had arrived at our place - were aboard the helicopter".