Regime forces surrounded a Turkish military observation post on Friday after overrunning nearby villages following their capture of the key northwestern town of Khan Sheikhoun from opposition fighters, the Syrian Observatory for Human Rights said.
The town of Morek, where the Turkish troops have been cut off, lies in the north of Hama province, part of the opposition-ruled region centered on neighboring Idlib province that has been under regime assault since late April.
"Regime forces have surrounded the Turkish observation post in Morek after capturing other towns and villages in this pocket," the Observatory said.
Opposition fighters had withdrawn from the area ahead of the army's entry into Idlib province’s Khan Sheikhoun on Wednesday.
Government forces overran the rest of the pocket, including the town of Kafr Zita without resistance.
The observation post in Morek is one of 12 the Turkish army set up along the front line between government forces and the opposition fighters last year.
Ankara vowed on Tuesday that it would not abandon any of the posts and warned Damascus "not to play with fire".
"We will do whatever is necessary to ensure the security of our soldiers and observation posts," Foreign Minister Mevlut Cavusoglu told reporters in Ankara.
The troops' mission was to oversee the establishment of a buffer zone agreed by Ankara and Moscow in September.
But the fighters failed to pull back from the zone as agreed and in April, government and Russian forces resumed intense bombardment of the region.