The Syrian army and its allied militia have launched a major assault on the rebel-held Syrian city of Zabadani, the Lebanese Shia group Hezbollah's television station said on Saturday.
It said heavy artillery and aerial bombardment were being deployed to capture the city, located north-west of the Syrian capital near the frontier with Lebanon.
The Syrian army has long sought to wrest control of Zabadani from Sunni militants. The city is close to the Beirut-Damascus highway that links the two countries and capturing it would be a major strategic gain for President Bashar al Assad's government.
Hezbollah, which is fighting alongside the Syrian army in Syria against the militants, has in recent months stepped up its assault on rebel outposts along the Qalamoun mountain region straddling the Lebanese Syrian border.
An announcement of the start of a major military campaign by the Syrian army and the Lebanese group to capture Zabadani had been expected in recent days.
The Syrian army has intensified its aerial bombardment of rebel positions in the area in the last few days, but the militants have dug in in the mostly deserted city.