The Britain-based Syrian Observatory for Human Rights says heavy clashes between soldiers and opposition fighters are underway west of Homs. The fighting is near a string of villages close to Syria's border with Lebanon, said the Observatory's director, Rami Abdul-Rahman.
The area is populated mostly by Shiite Muslims, who have supported President Bashar Assad's regime during Syria's two-year conflict.
Sunni Muslims dominate the opposition ranks, with many fighting on the side of the rebels.
The conflict started as peaceful protests against Assad's regime in March 2011 but turned into a civil war that has increasingly taken sectarian overtones.
More than 70,000 people have been killed, according to the United Nations.