It is reported by NDTV.
The helicopter crashed while landing on the drilling platform of the Indian oil and gas corporation Oil and Natural Gas Corporation Limited, 111 km off the coast of Mumbai.
On board were seven passengers and two crew members.
All of them were rescued, but four of them were taken unconscious to the hospital, where they later died.
The reasons for the crash are being investigated.
Earlier it was reported that six people were killed in the crash of a private helicopter Bell UH-1B in Logan County, US state of West Virginia.