Turkish customs authorities have detained a Russian cargo ship carrying grain which Ukraine says is stolen, Ukraine's ambassador to Turkey said on Sunday.

"We have full cooperation. The ship is currently standing at the entrance to the port, it has been detained by the customs authorities of Turkey," Ambassador Vasyl Bodnar said on Ukrainian national television.

Bodnar said that the ship's fate would be decided by a meeting of investigators on Monday.

Russia has not responded to the claims yet.