Syrian forces are massing north of Khan Sheikhoun in the rebel-held province of Idlib, days after the regime took control of the town.
The Syrian Observatory for Human Rights said loyalist fighters were preparing to advance an offensive against rebels in the area amid heightened tensions with neighbouring Turkey.
Idlib province on the Turkish border is one of the last to escape the control of the Damascus government. President Bashar Al Assad's forces, backed by Russia, launched a deadly bombardment on the area in April, which has killed around 900 civilians, according to the Observatory.
On Friday, they reclaimed a cluster of towns lost early in the eight-year-old war, driving out the last rebel fighters from the Hama countryside. They also took the strategic town of Khan Sheikhoun.
The Syrian army are now "preparing to continue their advance towards the area of Maaret Al Noman", a town some 25 kilometres (15 miles) to the north, Rami Abdel Rahman, the head of the UK-based monitoring group, told AFP.
That area has been under intense Russian and regime aerial bombardment and been depleted of almost all of its residents in the past two weeks in apparent preparation for the maneuver, the Observatory has said.
Both Khan Sheikhoun and Maaret Al Noman sit on a key highway running across the province that connects Damascus with Aleppo.
In Idlib city, which has until now largely been spared air strikes since the major bombing campaign began, a car bomb killed two and injured 11 on Saturday as regime air strikes hit its outskirts.
There was no immediate claim of responsibility.
Turkish troops have been deployed around the Idlib region in an attempt to set up a buffer zone to protect the area. Turkey, host to 3.6 million refugee Syrians, does not want further displacements over its border, with 3 million people residing in the province.
Around 400,000 have already been forced to flee their homes, according to the United Nations.
On Monday last week, regime aeroplanes targeted a rebel vehicle leading a Turkish military convoy down the main highway in the direction of their observation post in Morek.
Turkey's defence ministry claimed that three civilians were killed and 12 others wounded in the attack, which they said breached Ankara's agreements and co-operation with Russia.
The Syrian Foreign Ministry said the convoy had been carrying munitions to help rebels. The "aggressive" move of sending in the vehicles would not affect "the determination of the Syrian Arab Army to keep hunting the remnants of terrorists", a Syrian ministry source told state news agency Sana.
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. HTS, an alliance led by Syria's former Al Qaeda affiliate, since January, when rebel groups allied with Turkey were forced to cede overall control.
Buthaina Shaaban, adviser to Bashar Al Assad, on Friday accused Turkey of "turning the observation points into spots for transporting weapons and occupying a part of our land".
Turkey's President Recep Tayyip Erdogan is to visit Moscow on Tuesday for talks with his Russian counterpart Vladimir Putin.
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.
Syria's war has killed more than 370,000 people since starting with the brutal repression of anti-government protests in 2011.