AMMAN, Jordan — At least one Hezbollah guerrilla and five Syrian rebels have been killed in fighting in Syrian territory on the border with Lebanon, nearby Lebanese residents and Syrian opposition sources said on Sunday.

Hadi al-Abdallah of the Syrian Revolution General Commission said fighting broke out on Saturday after Lebanese Hezbollah fighters, who are in control of eight Syrian border villages, tried to expand their sphere by moving into three adjacent Sunni villages that were in the hands of the rebel Syrian Free Army.

"The Hezbollah force moved on foot and was supported by multiple rocket launchers. The  Syrian Free Army had to call in two tanks that had been captured from the Assad army to repel the attack," Abdallah told Reuters.

Shiite Muslim Hezbollah guerrillas based in the Bekaa Valley on the other side of the border, which is not demarcated, moved into the area last year. Four of the villages they had captured are inhabited by co-religionists while the other four villages are mixed with Sunni Muslim and Shiite residents.

Iranian-backed Hezbollah, one of Lebanon's strongest political factions, is a main ally of Syrian President Bashar al-Assad and says that dialogue between him and Syrian rebels will be the only way to defuse Syria's 23-month-old conflict.

Assad belongs to the minority Alawite sect, an offshoot of Shiite Islam that has dominated power in Syria since the 1960s. The border area near the town of Qusair, which is in the grip of the mainly Sunni rebels, is an important supply route for insurgents under siege in the central city of Homs.