BEIRUT (Reuters) - Syria's leading opposition group called on Wednesday for rebels across the country to send reinforcements to the strategic border town Qusair, where heavy fighting has drawn in fighters from Lebanon's powerful Hezbollah movement.
Rebels fighting to topple President Bashar al-Assad said air strikes and shelling rocked the small town on the Syrian-Lebanese border that has become a fierce battleground that could determine control of critical supply lines.
George Sabra, acting head of the opposition National Coalition, called on fighters to send arms and men to the area, citing concern over sectarian violence and "foreign invaders" from Hezbollah and Iran, the group's main patron.
"O sons of the Syrian revolution, foreign forces are invading your country ... They aim to destroy your lives, so rush to defend your nation," Sabra said in a written statement.
"Everyone who has weapons or ammunition should send them to Qusair and Homs to strengthen its resistance. Every bullet sent to Qusair and Homs will block the invasion that is trying to drag Syria back to the era of fear."
Assad's forces are intent on seizing Qusair in order to cement their hold on a belt of territory that connects the capital Damascus to Assad's stronghold on the Mediterranean coast, home to his minority Alawite sect, an offshoot of Shi'ite Islam that has largely supported him.
Seizing Qusair would also allow Assad to sever links between rebel-held areas in the north and south of Syria.
With Shi'ite Hezbollah leading the fight in Qusair, its involvement could drag Syria's civil war - which already pits mainly Sunni Muslim rebels, including radical Islamists and foreign fighters, against an Alawite-led army - into a more regional sectarian conflict.
Rebel leaders have warned of sectarian revenge attacks against Shi'ites and Alawites on either side of the Syrian-Lebanese border if rebels lose Qusair. Fighters speak of a tacit agreement among their units to launch village by village attacks should they be defeated in the town of 30,000.
Sabra warned that Hezbollah forces in Qusair could regionalize Sunni-Shi'ite tensions across the Middle East.
"The invasion will light a sectarian fire that will destroy relationships between countries in the region and their people. No one will benefit other than Israel."
Pro-Assad media have reported major advances for Hezbollah and state forces, and say that rebels have been given a route for retreat from the north. Rebels deny they have lost ground or are backing down.
Some opposition sources privately said they believed that the army, lead by Hezbollah ground units, has seized about 60 percent of the town. But they say rebels are fighting back hard, as they consider it a battle that could determine the fate of the uprising.
"If we lose Qusair, we lose Homs, and if we lose Homs, we lose the heart of the country," said Ahmed, a rebel speaking by Skype from Homs as explosions and gunfire crackled in the background.
One rebel source, who asked not to be named, said Assad and Hezbollah forces had cut most of the oppositions overland supply lines into Qusair. But he said the rebels were still able to bring some supplies and fighters in through secret tunnels.
An analyst close to Qatari officials said the Sunni Gulf state, which has funneled money and weapons to the opposition, was looking for new routes to send in supplies to Qusair.
Rebel forces from other parts of Syria appear to have taken seriously the call for support seriously.
The large Islamist Tawheed Brigade in the northern province of Aleppo published a video of a 30-car convoy it said was heading to Qusair.
Sedans and pickup trucks loaded with artillery and fighters sped down the highway, with rebels waving black Islamist banners shouting "God is Great."
(Reporting by Erika Solomon; Editing by Giles Elgood)