Syrian regime forces on Tuesday bombarded outskirts of the rebel-held town of Yabrud, the last opposition stronghold in the strategic Qalamoun region north of Damascus, a monitoring group said Al Arabiya reported.
"The next operation in Qalamoun is most likely going to be Yabrud, the last opposition stronghold," Rami Abdel Rahman, director of the Syrian Observatory for Human Rights, told AFP.
In an email, the Observatory said regime forces "pounded the outskirts of Yabrud and the Rima area and the outskirts of the town of Nabak."
The move towards Yabrud comes after government forces, reportedly backed by fighters from Lebanon's Hezbollah movement and members of a Syrian pro-regime militia, took Nabak.
The capture comes as part of a broad regime campaign to seize the mountainous Qalamoun region, severing rebel supply routes that run across the nearby border with Lebanon.
The regime has now taken control of the towns of Qara, Deir Attiya and Nabak, all of which lie along the strategic Damascus-Homs highway.
The highway had been closed by the fighting, but authorities are expected to reopen it shortly.
Opposition fighters have taken control of the historic Christian town of Maalula, also in Qalamoun, but Yabrud remains the only real stronghold still in rebel hands.
Abdel Rahman said rebel forces were also present in a handful of villages in the region, but that Yabrud represented the last major strategic prize in Qalamoun for the regime.
Syrian state media announced Monday that regime forces had seized control of Nabak and were "pursuing remaining pockets of terrorists in the outskirts of the town."
The regime uses the word "terrorists" to refer to all members of the opposition.
The Qalamoun region has long been a rear base for the opposition, but the regime's advance is likely to cut supply routes for weapons and fighters.
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