ISTANBUL (AFP) - A five-year-old girl was killed and three women were injured when their car plunged into the sea while boarding a ferry in Istanbul, local media reported on Sunday.

The ferry began pulling away from the dock on Saturday in the tourist district of Sirkeci as the last vehicle - carrying four people - was trying to board, the Hurriyet newspaper said.

The ferry's hatchway was not properly locked when the ferry started moving, causing the car to slide backwards and fall into the water.

The girl's mother and another passenger managed to get out of the car before it completely sank. The girl, identified as Ece Su Yilmaz, and her grandmother had to be lifted out of the water by divers.

Yilmaz died in hospital while her grandmother remains in intensive care.

The captain of the ferry and two crew members were arrested on Sunday on charges of involuntary murder.