Syrian regime forces have shelled the Rankus area ahead of an operation to retake the town, one of the last rebel-held regions in the Qalamun area, a monitoring group said Tuesday.
Al-Manar television, which belongs to the pro-Syrian regime Lebanese group Hezbollah, also reported that the Syrian army had begun an offensive against Rankus.
A military source, meanwhile, told AFP that regime forces had taken a hilltop position by Rankus and were surrounding the town.
The Qalamun region is strategic because it lies along the border with Lebanon and the main highway between Damascus and the city of Homs runs through it.
"The area of Rankus in Qalamun has been under heavy shelling and continuous air raids since Monday, ahead of a plan to storm it," Syrian Observatory for Human Rights chief Rami Abdel Rahman told AFP.
He said Hezbollah was leading the operation by regime forces in the region, where the army has gradually recaptured control of almost all areas formerly held by the rebels.
Fighters from pro-regime militias were also involved in the battle, which comes after the regime secured a major victory by capturing the rebel bastion of Yabrud nearby on March 15.
With the fall of Yabrud, rebel forces lost most of their supply routes crossing the border into Lebanon.