The Transport Ministry says the Sierra Leone-flagged cargo ship Karam 1 sank late Monday after colliding with the Dutch tanker Alessandro DP, 10 miles (16 kilometres) off Cape Emine.
Five sailors of the cargo ship's of crew of nine Syrians and an Egyptian were rescued and five are missing.
The cargo ship was loaded with scrap metal en route to Istanbul, while the tanker was empty and heading to the nearby Bulgarian port of Varna.