A cargo ship with 12 crew on board has sunk after a thunderstorm in the Black Sea off Turkey, maritime authorities say.

Three people have been rescued from the wreck, the authorities said of Tuesday's accident.

The ship, which was carrying a cargo of coal, sank off the small port of Sile, northeast of Istanbul.

Rescue boats were dispatched to find the missing crew members - 11 Ukrainians and a Russian - and three had been saved, Turkey's maritime authority said, according to the the Anatolia news agency.

The Volga-Balt 199 freighter, registered in Saint Kitts and Nevis, sent out a distress signal before disappearing off radar screens.

The Istanbul coast guard dispatched rescue services and a helicopter to the scene, Anatolia said, adding that the ship had been travelling from Russia to Turkey's popular Mediterranean resort of Antalya.

Another freighter, the BBC Adriatic, was also in difficulty off the coast of Kilyos, a beach resort in northwest Istanbul, according to the maritime authority.

The heavy thunderstorm has disrupted sea traffic in Istanbul.

Source: Agencies