Continuing its violations of last year's cease-fire agreement, the Syrian regime on Thursday attacked a Turkish military observation post in northwestern Syria with harassment fire, officials told Anadolu Agency. 

Regime jets fired heavy machine guns near observation point no. 8 in Maaretinuman, in southeastern Idlib -- a zone where acts of aggression are forbidden -- they said, speaking on condition of anonymity as they were not authorized to speak to the media. 

The harassment fire did not cause any damage, they added. 

Observation post 8 in Sirman is located north of Khan Shaykhun, a town regime forces battered on Wednesday. 

The Bashar al-Assad regime struck Khan Shaykhun at midday on Tuesday backed by Iranian-backed foreign terrorist groups and Russian special forces. 

There are still a small number of opposition fighters and anti-regime armed elements in the area. 

On Monday, regime airstrikes targeting a Turkish convoy en route to observation post no. 9 killed three civilians and injured 12 others.

- Violated cease-fire

Turkey and Russia agreed last September to turn Idlib into a de-escalation zone where acts of aggression are expressly prohibited. 

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

The Syrian regime and its allies, however, have consistently broken the terms of the cease-fire, launching frequent attacks inside the de-escalation zone. 

The de-escalation zone is currently home to some 4 million civilians, including hundreds of thousands recently displaced by regime forces throughout the war-weary country. 

Syria has been locked in a vicious civil war since early 2011, when the Assad regime cracked down on pro-democracy protests with unexpected ferocity. 

Since then, hundreds of thousands of people have been killed and more than 10 million others displaced, according to UN officials.