Terrorists have reportedly fired mortar shells from a planned buffer zone in the northwestern Syrian province of Idlib, killing two Syrian soldiers.

The attack saw several projectiles being fired “at an army position in nearby Hama province" late Saturday, the so-called Syrian Observatory for Human Rights said on Sunday.

Shells were also fired from elsewhere inside the de-escalation zone, but did not result in any casualties, the London-based group added.

The zone has been planned out by Russia and Turkey, which sides with anti-Damascus groups. Under the plan, all militant and terrorist groups must hand over their heavy weapons by October 10.

"This is the first clear violation of the deal since the heavy weapons were withdrawn. This area is supposed to be clear of heavy weapons, including mortar shells," said Observatory head Rami Abdel Rahman.

Syria’s Al Watan paper reported similar violations. It said that western parts of the neighboring Aleppo Province were being hit by "rocket fire and shelling with heavy weapons, which were supposed to be pulled out from the area."

Ankara's agreement with Moscow forestalled an imminent offensive to liberate Idlib where several Turkish-backed militant groups are based.

The Turkey-Russia deal also calls for the removal of all members of Takfiri and other terrorist groups from the demilitarized zone but they have refused to submit to the requirement.

Idlib Province contains the largest concentration of Takfiri terrorists who have been driven out of the rest of the country by the Syrian army and its allies.

Damascus has clearly asserted that the Idlib agreement is only “temporary,” and that the province should ultimately come under the government control.

Russian Foreign Minister Sergey Lavrov on Friday confirmed that the agreement is temporary and that the Syrian government should ultimately regain control over the entire territory.

"Indeed, it is a temporary agreement. The end of the story will be only the Syrian people regaining control of the country and all those who are staying in Syria, especially those who were never invited there, leaving the country. It is clear for all," he told France's Le Figaro in an interview.