Hizbullah backed by Syrian forces controlled on Thursday strategic heights in the Syrian region of Qalamoun that abuts Lebanon's eastern border, the Syrian Observatory for Human Rights said.
The control of the area on the outskirts of Assal al-Wared came following heavy clashes with al-Qaida linked al-Nusra Front, it said in a statement.
The battles were accompanied by heavy shelling by Syrian warplanes.
The Britain-based Observatory stressed that there were casualties from both sides.
Hizbullah's Secretary General Sayyed Hassan Nasrallah said in a televised speech late Tuesday that his group will attack militants in Qalamoun, stressing that "time will tell" when the battle will become full blown.
He added that there will be no formal announcement before the widely anticipated battle begins.
Nasrallah vowed that his group will continue fighting in Syria along with President Bashar Assad's forces.