Aankara: A Turkish soldier was killed and three others have been injured when the Syrian government fired on their observation post in the last rebel-held province of Idlib, Ankara said Friday.
The "mortar and cannon shells" launched Thursday were a deliberate attack, the Turkish defence ministry said in a statement.
Turkey has 12 observation posts in Idlib, in northwestern Syria, where they are trying to maintain a tenuous ceasefire.
Idlib is one of several "de-escalation zones" agreed under the Astana peace process last September that brought together Russia and Iran, who support the Syrian government, and Turkey, which backs certain rebel groups.
But Damascus has intensified its attacks since late April, leading to fears in Turkey of a mass exodus of refugees from the province, which is home to some three million people.
The Turkish ministry said it responded Thursday with its own bombardment, while its army chief summoned Russia's military attache to warn of "severe" consequences for future attacks.
President Recep Tayyip Erdogan accused the Syrian government in May of trying to sabotage Turkey's cooperation with Russia as they seek a solution to the eight-year conflict.