Turkish Prime Minister Recep Tayyip Erdogan says a Syrian plane forced by Turkish fighter jets to land in Ankara was carrying Russian-made defence equipment and munitions destined for the Syrian military.
Syria and Russia deny the plane was carrying illegal cargo.
"Passenger aircraft cannot carry ammunition and defence equipment," Mr Erdogan said, adding, "unfortunately there was such equipment on board".
Turkish jets forced the plane, coming from Moscow, to land at Esenboga airport in Ankara on Wednesday night.
Turkey said previously it had received an intelligence tip-off that it had illegal cargo on board.
"This was equipment and ammunition that was being sent from a Russian agency ... to the Syrian Defence Ministry," Mr Erdogan said
"Their examination is continuing and the necessary will follow," he added.
