Syrian army troops pushed deep into a pocket of territory in the country's north-west where they encircled rebels and a Turkish military post, seizing towns the insurgents have held for years, state TV and a monitor said on Friday.
The army has imposed "a choking siege" on the cluster of towns, with much of it coming either under army control or within firing range, state-run Ikhabriya TV said.
Soldiers captured a dozen hills, expanding state control of a main highway that runs through the area and stretches from the capital Damascus to Aleppo city, it added.
The advance follows the capture of the strategic town of Khan Sheikhoun in the south of Idlib province on Wednesday. The town sits on the Damascus-Aleppo highway.
The Syrian Observatory for Human Rights said pro-government forces, backed by Russia, retook the town of Kafr Zita from rebels who had controlled it since 2012. A Turkish military post in the nearby town of Morek was now also encircled, the UK-based war monitor and state TV said.
Morek lies in the north of Hama province, part of a rebel-held region centred on neighbouring Idlib province that has been under government assault since late April.
The rebels had withdrawn from the area ahead of the army's entry into Khan Sheikhoun and government forces overran the rest of the pocket without resistance.
Battles for the area and attacks in other parts of Idlib have forced tens of thousands of civlians to flee in recent days towards the border with neighbouring Turkey.
The observation post in Morek is one of 12 set up by the Turkish army along the front line between government forces and the Hayat Tahrir Al Sham (HTS) group and its rebel allies last year.
Speaking in the Lebanese capital on Friday, Turkish Foreign Minister Mevlut Cavusoglu said "our observation point there is not cut off and nobody can isolate our forces and our soldiers".
"We are there, not because we can't leave but because we don't want to leave," he told reporters in Beirut, adding that the issue was being discussed with Damascus allies Russia and Iran.
Mr Cavusoglu vowed on Tuesday that Turkey 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," he said.
The Turkish troops' mission was to oversee the establishment of a buffer zone agreed by Ankara and Moscow in September.
But HTS failed to pull back from the zone as agreed and in April, government and Russian forces resumed intense bombardment of the region.
Nearly 900 civilians have been killed since then, according to the Observatory.
More than 400,000 have fled their homes, the United Nations says.
The government said on Wednesday that it had opened a humanitarian corridor for civilians who wanted to leave northern Hama and southern Idlib, promising shelter, food and medical care for those who did so.
The Idlib region, which sits on the Turkish border, is now the last major stronghold of opposition to the Russia-backed government of President Bashar Al Assad.