Syrian rebels withdrew from a town in southern Idlib province and from their last remaining territory in neighbouring Hama province after government troops advances in the area, the Syrian Observatory for Human Rights and local activists said.
It marks an important gain for President Bashar al-Assad into the northwestern region which is the last major rebel stronghold in Syria. Backed by Russia, Syrian government forces have been attacking the region since late April.
Syrian government forces advanced into the town of Khan Sheikhoun in southern Idlib late on Monday. The town had been in rebel hands since 2014. The opposition's territorial foothold in neighbouring Hama province dates back to the earliest days of the eight-year-long conflict.
Russian-backed Syrian government advances around Khan Sheihkoun had threatened to encircle rebel fighters in their last remaining territory in northern Hama, including the towns of Latamneh and Kafr Zeita.
The rebels quit those towns, local activists said.
The Observatory said Syrian rebels who had stayed behind in that area had gathered at a Turkish military position in the town of Morek, in the territory abandoned by the rebels.
Khan Sheikhoun was targeted in sarin gas attack in 2017 that prompted US missile strikes against Syria.
An investigation conducted by the United Nations and the Organisation for the Prohibition of Chemical Weapons said the Syrian government was responsible for releasing sarin on the town on April 4, 2017. Damascus denies using such weapons.
The latest Syrian government offensive in the northwest has forced hundreds of thousands of people to flee towards the Turkish border.
The US-based Union of Medical Care and Relief Organizations (UOSSM), which supports medical facilities in the northwest, says more than 730 civilians had been killed by government or Russian forces since late April.
The UN Office for the Coordination of Humanitarian Affairs has said more than 500 civilians have died in hostilities. (Writing by Tom Perry Editing by Andrew Heavens)