A massive search operation is continuing for "hundreds" of missing migrants after at least 78 drowned when a fishing boat sank off the coast of Greece.

Officials said 104 survivors were rescued after the vessel capsized about 50 miles from the southern coastal town of Pylos.

 

But charity Alarm Phone, which operates a network supporting rescue operations and received frantic calls from some of those on board, said up to 750 people may have been on the vessel.

Greek officials said the boat got into difficulties when its engine stopped and it began veering from side to side. It then capsized and sunk at around 2am on Wednesday.