Syrian troops seized control Monday of a village near the strategic rebel bastion of Yabrud as they pushed closer to the town near the border with Lebanon, state television said.
The Syrian Observatory for Human Rights monitoring group, meanwhile, said the army, backed by Lebanon's Shiite Hezbollah, was "advancing" in the area, but that "fierce battles are still ongoing there."
Al-Qaeda's Syria affiliate, Al-Nusra Front, is playing a major role in the fighting, said the Britain-based Observatory.
State television said the army "took control of Sahel village in the Yabrud area, after killing several terrorists."
Sahel is only six kilometres (four miles) from Yabrud, a key rebel stronghold in the Qalamoun mountains, north of Damascus, and near the Lebanese border.
For nearly three weeks, the Yabrud area has come under intense, daily bombardment.
The battle for Yabrud is crucial for Hezbollah, which accuses rebels of using it as a gateway to sending car bombs to target its strongholds in eastern Lebanon and southern Beirut.
Observatory director Rami Abdel Rahman described Sahel as "a key entry point to Yabrud" but stressed that the army had not taken it yet.
"The army does not want to take Yabrud. It's objective is to seize the surrounding villages and hills, to completely besiege the town."
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The Syrian army has used the siege tactic in several towns and cities from the onset of the nearly three-year war that has now killed an estimated 140,000 people.
Hezbollah's television channel Al-Manar screened footage from Sahel on Monday afternoon. One of its journalists did a standup from the village, while gunmen and armoured vehicles could be seen in the background.
The reporter said the capture of Sahel was aimed at "tightening the noose around the main (rebel) bastion in Yabrud."
Hezbollah is fighting to try to cut off the road linking Yabrud to Arsal in eastern Lebanon, whose population supports the Syrian revolt.
But according to a Lebanese source with close links to Syria's rebels, the insurgents are still in control of the road linking Arsal to Yabrud, and several others in the region.
In spring 2013, Hezbollah acknowledged sending fighters into Syria to support the Syrian army, exacerbating divisions in Lebanon between pro and anti-Damascus camps.
Hezbollah says it is trying to defend Lebanon from an "extremist" threat, while its critics say the Shiite party has pulled the perils of Syria's war into Lebanon.
On Monday, four people were injured when five rockets launched from Syria hit a Hezbollah-dominated area of eastern Lebanon, a security source told AFP.
The rockets landed around the villages of Brital and Khodr.
Jihadist groups frequently claim responsibility for cross-border rocket attacks on eastern Lebanon, which they say are in revenge for Hezbollah's intervention in Syria.