The militants captured the villages of al-Jabin and Tel Melah in northern Hama province in early June.
The Syrian army managed to advance in the area as Syrian and Russian warplanes targeted militant positions and after several days of preparatory fire, Reuters reported.
The targeted area is part of the last major foothold of the militancy against President Bashar al-Assad, who has vowed to take back "every inch" of Syria.
The Syrian army's operations are responses to militant violations of ceasefire agreements.
Under a deal reached following a meeting between Turkish President Recep Tayyip Erdogan and his Russian counterpart Vladimir Putin in September, all militants should have withdrawn from the demilitarization zone by October 15.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.