A Turkish observation post in Syria's Idlib region was attacked with mortar fire and shelling from an area controlled by Syrian government forces, causing damage but no casualties, the Turkish Defence Ministry said on Sunday.
The ministry said its forces immediately retaliated with heavy weapons and it made representations to Moscow over the incident.
It did not specify when the shelling occurred, but said the attack was launched from what it named the Tall Bazan area and it was assessed to be deliberate.
Russia, which supports Syrian President Bashar al-Assad in his country's civil war, and Turkey, long a backer of the opposition, co-sponsored a de-escalation agreement for the area that has been in place since last year.
On Thursday Russia and Syria gave sharply conflicting accounts of a previous attack on a Turkish outpost.
