Syrian regime forces advanced against militants Saturday on the edge of the northwestern province of Idlib, the last outside government control, a monitor and the state news agency said.
Government and allied forces backed by Russian warplanes have since Monday been battling militants fighters in an area straddling the border between Idlib and Hama provinces.
The fighting, which could signal the start of a major offensive to seize Idlib province from militants dominated by a former Al-Qaeda affiliate, escalated on Thursday.
On Saturday, Syrian troops advanced, seizing several villages and surrounding areas, the Syrian Observatory for Human Rights, a Britain-based war monitor, said.
State news agency SANA said Syrian forces had taken control of five villages, areas and "strategic hills" in the northeast of Hama province.
An AFP correspondent said civilians continued to flee areas near the battle zone, heading north towards the provincial capital of Idlib with their belongings piled high on pickup trucks.
"We were the target of strikes more than once - we couldn´t stay," said Abu Ahmed, a man in his sixties from the southeast of Idlib province, fleeing with his family in a pickup.
"I don't know how to say how I feel, leaving my land and home at my age. We are leaving without even knowing where we're headed."
In the Maaret al-Numan area, some people have put up tents, pots and pans piled at the entrance flaps.
"We escaped for the sake of the children. They were terrified by air raids and strikes," said Abu Khaled, a bearded man in his thirties wearing a red and white checkered keffiyeh headscarf.
The father-of-four, originally from Hama province, had already fled once with his family - to Idlib, where they lived in a camp for the displaced.
Since Thursday, the clashes have killed 32 soldiers and allied members of paramilitary units, as well as 29 militants from militant groups or from former Al-Qaeda affiliate Fateh al-Sham, the Observatory said.
Twenty-one civilians have also died.
Government forces first aim to take control of the southeast of Idlib province, Observatory head Rami Abdel Rahman said.
This would allow the regime to have full control of a road that links the capital Damascus to the government-held second city of Aleppo.
Russia intervened on the side of President Bashar al-Assad´s regime in 2015, helping it to take back control of swathes of territory including Aleppo.
The forces of Syrian General Suheil Hassan, on the front lines of the battle against Daesh in the east of the country, are leading the Idlib offensive, the Observatory said.
"After finishing off IS, the regime's forces are concentrating their operations on Idlib's militants," Abdel Rahman said.
The war in Syria has killed more than 340,000 people and displaced millions from their homes since it began in 2011 with the brutal repression of anti-government protests.