An air strike by Syrian government forces in Idlib killed nine Turkish soldiers and severely wounded several others, the local governor in the southeastern province of Hatay said late on Thursday.
Rahmi Dogan said the wounded soldiers were brought to hospitals in Turkey.
However the Syrian Observatory, a war monitor, reported at least 34 Turkish soldiers were killed in air strikes.
Turkey has sent thousands of troops and heavy military hardware into northwest Syria's Idlib province to back rebels looking to hold back an offensive by Syrian government and Russian forces aimed at taking back the rebel stronghold.
Two sources told Reuters that President Tayyip Erdogan held an emergency meeting with his staff due to the attack, which they said was carried out by either Syrian government forces or their ally Russia.