BEIRUT // A fierce battle along the Syria-Lebanon border between Hizbollah and Syrian rebels led by Jabhat Al Nusra has fueled fears that Lebanon could be further dragged into Syria’s messy civil war.

The Lebanese army, which has skirmished with Syrian rebels in recent months, could find itself drawn into the fight.

There are also fears that rebels may seek to carve out territory in Lebanon and that fighting between Hizbollah – staunch allies of Syrian president Bashar Al Assad – and Sunni militias could provoke sectarian violence here.

So far, the scope of the battles, which began on Monday in the western Syrian region of Qalamoun in the barren, mountainous area that stretches across the border, remains unclear.

The UK-based Syrian Observatory for Human Rights said on Wednesday that four Hizbollah fighters – including a commander – had been killed in Qalamoun along with six rebels.

Hizbollah’s Al Manar television station also claimed on Wednesday that the group had killed three rebel commanders during an attack on a gathering of leaders from Al Nusra – Al Qaeda’s Syria affiliate – and other insurgents, in the Syrian town of Al Juba near the Lebanese border.

“Dozens” of Al Nusra militants were killed in ambushes by Hizbollah and the Syrian army in recent days, according to Al Manar, which said some of the fighting had taken place inside Lebanon.

Both pro-rebel and pro-Hizbollah media outlets circulated identical pictures of camouflage-clad corpses on the battlefield, lying face down in the dirt. The pro-rebel outlets claimed that the corpses were those of Hizbollah fighters, while Al Manar said they were Al Nusra militants.

Last week, before the fighting in Qalamoun started, Al Nusra released pictures of its forces assembling, with some of the rebels dressed in army fatigues. Others were dressed all in black.

On Tuesday, the rebels said they had formed a new Jaysh Al Fateh alliance in Qalamoun, seemingly modelled after a coalition of the same name that has driven recent rebel gains in Idlib province. The Jaysh Al Fateh alliance in Idlib – dominated by Al Nusra – was formed in late March and succeeded in driving regime forces from their strongholds in the province in just weeks.

“The fact that Jabhat Al Nusra and rebel forces appear to be consolidating under the umbrella of Jaysh Al Fateh in Qalamoun is an important indicator that Nusra’s demonstrated model for success in Idlib has gained traction on other battle fronts,” said Jennifer Cafarella, an analyst of the Syrian conflict at the Washington-based Institute for the Study of War.

“The significance in some ways of Qalamoun is that it’s a component of a wider shift in how Syrian rebels are negotiating their relationships with one another and how the Syrian rebels are attempting to unite their efforts against the Assad regime,” she added.

Still, Ms Cafarella said, it appears Hizbollah and the Syrian government have the upper hand in Qalamoun and that the rebels will likely turn to guerrilla warfare.

An official from the rebel-aligned Qalamoun media office, who identified himself as Abu Yahya, said the names of the rebel groups in the new Jaysh Al Fateh alliance will be disclosed in the coming days.

The outbreak of violence on the border – and the lead role taken by Hizbollah – threatens to further entangle Lebanon in Syria’s civil war and drive domestic sectarian tensions.

Hizbollah’s intervention in Syria has been sharply criticised by its opponents in Lebanon, but the group’s leader Hassan Nasrallah argued on Tuesday that it was necessary to protect Lebanon.

“The [Lebanese] state is incapable of doing this,” he said during a speech.

“If we waited for consensus, these armed groups would have already been in many areas of Lebanon.”

Despite the increased level of violence in recent days, Mr Nasrallah said Hizbollah had not yet waged its major campaign against the rebels along the border and that the group would not announce the attack when it came.

Both Al Nusra and ISIL have been seen as having aspirations in Lebanon and both have claimed suicide bombings inside the country.

In a joint offensive last August, ISIL and Al Nusra fighters seized control of the Sunni border town of Arsal. They were forced out of the town by the Lebanese military after five days but retained positions within striking distance of Lebanese border towns like Arsal, Brital, Tfail and Ras Baalbek.

Since then, both Hizbollah and the Lebanese army have had skirmishes with Sunni militants on the border.

In the latest offensive, there is a risk that Al Nusra will try to grab Lebanese territory once again or that their battle with Hizbollah will further inflame sectarian tensions in Lebanon, where the group enjoys a level of support among certain segments of the Sunni community.

“I think their end game is to pull the Sunni community under their wing,” said Phillip Smyth, a researcher at the University of Maryland who focuses on the Syrian conflict.

“This is the longer term threat that Hizbollah sees and that Lebanon sees: What happens if and when you have a section of the Lebanese Sunni community that says ‘well, I guess Al Nusra is going to be the sharp tip of our sword because we don’t like Hizbollah’?”

Ms Cafarella said ISIL and Al Nusra might look to destabilise Lebanon to create an opportunity for their expansion.

Al Nusra has warned Lebanon’s army not to get involved in the fighting in Qalamoun.

In a video released by the group on Tuesday, Lebanese hostages seized last year warned that if the army gets involved, the hostages will “pay the price”.

However, Abu Yahya, the Qalamoun media office official, downplayed concerns that rebels will seek to establish a beachhead in Lebanon.

“The aspirations of the mujahideen are to liberate the land [in Qalamoun] and defeat the Hizbollah terrorists,” he said. “Their battle is only with Hizbollah.”

Abu Yahya added that ISIL – which had previously cooperated with Al Nusra in Qalamoun while warring with them elsewhere – was not a participant in the battle.

foreign.desk@thenational.ae