Coastguard personnel overnight Saturday to Sunday raided the Mongolian-flagged "Ole" vessel after a tip-off that migrants were being carried on board.
The coastguard picked up 71 migrants on board the ship off the southeastern Turkish city of Mersin and captured 279 others waiting their turn at the port to board the vessel, Anatolia said.
It said the migrants, including women and children, were seeking to reach European Union countries, in particular Italy.
Signup to our newsletter and follow us on Facebook and Twitter!
Police detained 10 crewmen and seized the inflatable boats used to transfer the migrants to the ship.
Turkey, which already hosts 1.8 million Syrian refugees from the civil war, has become a key transit point for migrants seeking a better life in Europe.
Mersin has become known as an increasingly important hub for Syrian migrants, with local authorities saying that 1,754 illegal migrants were apprehended at sea off the port last year.
Turkish authorities have stepped up operations on migrant boats amid a surge in the numbers attempting the perilous crossing, following the Mediterranean's worst migrant disaster recently in which as many as 800 people drowned off Libya.