Syrian troops backed by Hezbollah fighters made fresh gains in the strategic Qalamun region near the border with Lebanon Saturday, seizing two villages from rebels, a military source told AFP.
Controlling Qalamun is crucial for President Bashar al-Assad's forces as this would stop the flow of weapons and fighters entering Syria from Lebanon.
The Lebanese Shiite group Hezbollah says deadly car bombs targeting the movement in Lebanon were rigged with explosives in the Qalamun area.
"The army took control this morning of the villages of Ras al-Maarra and Flita, after bombing the last groups of armed terrorists there," the source said.
Assad's troops backed by Hezbollah have been assaulting rebel positions in Qalamun, north of Damascus, since November.
In mid-March they seized the rebels' last major stronghold in the region, the town of Yabrud, and have since moved on rebel-held villages closer to the border.
The military source called the latest advance "a new step towards closing off the border with Lebanon".
Though capturing Flita and Ras al-Maarra has not completely sealed the border, "any success... helps seal the border more tightly, at least at the main crossing points that (the rebels use) to transport vehicles", he added.
Rebels in the two villages were overwhelmed by superior firepower, an activist in the region, Jawad al-Sayed, said.
Signup to our newsletter and follow us on Facebook and Twitter!
"The fighters are very visible from the sky, and they are being hit from afar, whether by planes or tanks."
The fall of the two villages forced around 700 Syrians to flee across the border to the town of Arsal, Lebanon's National News Agency reported.
"The Lebanese army is checking their identities and is preventing armed men (rebels) from entering Lebanon," it said.
Arsal residents support the revolt against Assad, and the town already hosts tens of thousands of Syrian refugees.
Smuggling routes used by opposition forces to move fighters and weapons between Lebanon and Syria pass through the Arsal area.
The Syrian Observatory for Human Rights said rebels now control only a few towns in the Qalamun region, including Rankus and the historic Christian town of Maalula.
Despite the army recapturing the two villages, "it will be very difficult to control the whole border", said Observatory director Rami Abdel Rahman.
"The army and Hezbollah would need to deploy fighters all along the border, which is impossible," he told AFP.
Local rebel commander Ahmed Nawaf Durra was killed in the fighting, the Britain-based monitoring group said.