Turkey struck dozens of Syrian government targets after five of its soldiers were killed in Syria's Idlib region, a move that could test ties between Moscow and Ankara.
President Tayyip Erdogan said 30-35 Syrians were "neutralised" in Turkey's response to intense shelling of its soldiers in Idlib, the last major Syrian rebel stronghold.
Turkey has reinforced Idlib, which lies just across its southern border with Syria, in a challenge to Damascus and its Russian backers.
Syrian President Bashar al-Assad's forces, backed by Russian air power, have made large advances in Idlib, prompting Turkey to warn it may launch a military operation there.
"We have responded in kind to these attacks and will continue to do so, " Mr Erdogan said.
A Turkish security official said the shelling that killed the soldiers occurred near Saraqeb, at the junction of two main roads that Damascus seeks to control.
Turkey may launch a military operation in Syria's north-western Idlib region unless fighting there is quickly halted, President Recep Tayyip Erdogan said yesterday as attacks by Syrian government forces risked a new wave of refugees.