At least one civilian was killed on Sunday in attacks by the Syrian regime and pro-regime terrorist groups in Syria's northwestern Idlib de-escalation zone.

The regime and Iranian-backed terrorist groups have been firing artillery into the villages which are situated inside the de-escalation zone, the parameters of which were laid down in a recent agreement between Turkey and Russia.

Speaking to Anadolu Agency, Mustafa Hajj Youssef, director of the White Helmets civil-defense agency, said the attacks targeting Idlib's southwestern villages also left two civilians injured.

Youssef said that the wounded were taken to a nearby hospital.

After a meeting in Russia's coastal city of Sochi between President Recep Tayyip Erdoğan and his Russian counterpart Vladimir Putin on Sept. 17, the two sides agreed to set up a demilitarized zone -- in which acts of aggression are expressly prohibited -- in Idlib.

Under the terms of the deal, opposition groups in Idlib will remain in areas in which they are already present, while Russia and Turkey will carry out joint patrols in the area to prevent a resumption of fighting.

Syria has only just begun to emerge from a devastating conflict that began in 2011 when the Assad regime cracked down on demonstrators with unexpected ferocity.