BEIRUT - As fighting rages just across the border, Lebanese are giving signs of joining the battle on rival sides of Syria's civil war - Sunnis on the side of the rebels, Shiites on the side of the regime - raising fears that Lebanon will be dragged into the conflict.

Two influential Lebanese Sunni clerics this week called on members of their community to wage "holy war" in Syria to defend their brethren. They accused Lebanon's Shiite Hezbollah group of sending fighters to attack Syrian Sunnis, who make up the backbone of that country's rebellion.

Around two dozen men lined up Tuesday in the office of one of the clerics in the southern coastal city of Sidon to join the jihad.

In recent days, tensions have been fueled by heavy fighting inside Syria close to the border with Lebanon, where regime forces have made strong gains in a campaign to secure a corridor from the capital, Damascus, to the Mediterranean coast.

The Syrian military has been helped in the fight by Shiite Lebanese fighters who are supported by Hezbollah. The powerful Lebanese militant group says it is not sending fighters but supports the so-called "popular committees" that have joined the fighting to defend fellow Shiites in Syria.

Rockets from Syria have hit mostly Shiite areas in Lebanon on a daily basis, apparently from Syrian rebels in retaliation for Lebanese Shiite help to the regime. Rockets killed at least two people this week. There are also fears that Islamic militants among the Syrian rebels could carry out direct attacks in Lebanon in revenge for Hezbollah's support of the regime.

"Lebanon is on the edge of the cliff," lawmaker Sami Gemayel warned on Tuesday. "We are dragging the conflict from Syria into our country. It's like the border between the two countries no longer exist."