Clashes erupted when the Syrian army seized a position held by the Jaish al-Izza militants near Halfaya village on the edge of the northwestern Idlib province, the so-called Syrian Observatory for Human Rights said, Reuters reported.
At least 22 members of the militant group were killed in the clashes, and dozens more were wounded, the highest casualty toll of militants in the northwest in many months, it said.
According to the Observatory, government forces moved in to take a high building held by the rebels in a rural area of neighboring Hama province.
The Halfaya village, where the clashes broke out, is located in a planned buffer zone, which surrounds Idlib and also parts of the adjacent provinces of Aleppo and Hama.
Under a deal reached following a meeting between Turkish President Recep Tayyip Erdogan and his Russian counterpart Vladimir Putin in September, all militants must have withdrawn from the demilitarization zone by October 15.
However, al-Qaeda-linked Takfiri terrorists said they refuse to either leave the buffer zone or hand over their weapons.
Moscow believed that the 15-20 kilometer buffer zone would help stop attacks from Idlib-based militants on Syrian army positions and Russia's military bases in the flashpoint region.
However, Russian Foreign Ministry spokesperson Maria Zakharova said Thursday that terrorists were continuing to make provocative acts in the demilitarized zone.