BEIRUT // Hizbollah has declared war on ISIL after the extremists launched an offensive on its positions inside Lebanon this week.

The Shiite militant group has been fighting Al Qaeda-linked Jabhat Al Nusra and allied rebel groups for more than a month along the border between Lebanon and Syria, but its declaration of war with ISIL opens up a new front.

“The battle with ISIL has begun,” Hizbollah leader Hassan Nasrallah declared on Wednesday, vowing to erase the threat ISIL posed to Lebanon and blaming the extremist group for starting the fight.

His televised address came a day after ISIL fighters attacked a Hizbollah position outside the Bekaa Valley border town of Ras Baalbek in Lebanon’s north-east.

Hizbollah’s Al Manar TV station reported that 50 ISIL militants were killed and 80 wounded as the attack was repulsed.

Footage broadcast by Al Manar showed corpses of ISIL fighters strewn on the ground in the barren hills along the border.

The bodies were surrounded by automatic rifles, machine guns, rocket-propelled grenades and sacks of ammunition that Hizbollah said were captured from the militants. Pieces of paper among the captured weapons bore the ISIL logo.

The reported death toll suggests the attack was ISIL’s most significant push into Lebanon since the group stormed and briefly captured the Sunni border town of Arsal last August in a joint offensive with Al Nusra.

In his speech on Wednesday, Nasrallah described the fight on with ISIL as “one of the fiercest battles” .

“They will definitely be defeated,” he said. “But this needs time, and we are waiting patiently to achieve this goal.”

In May, Hizbollah launched an operation to dislodge Al Nusra and its allies from Syria’s Qalamoun region along the Lebanese border. Some of the fighting along the porous border took place inside Lebanon.

Al Manar reported on Monday that Hizbollah had captured 90 per cent of Al Nusra’s military posts in the fight, and had seized 64 per cent of the territory formerly occupied by Nusra and ISIL.

However, ISIL was not involved in those battles.

While ISIL and Al Nusra have fought each other elsewhere in Syria, the two groups cooperated along the Lebanon-Syria border for a long time. Last August, they captured Arsal in a joint assault, holding it for several days before being pushed out by the Lebanese army.

Since then, their relationship has deteriorated, reflecting the hostility between the two groups as seen elsewhere in Syria.

As the Nusra-led Jaysh Al Fatah rebel coalition was battling Hizbollah on the border, the alliance also declared war on ISIL in the region last month.

ISIL’s ambitions along the Lebanese border are not clear.

The region is a distant and lonely outpost for the group, far removed from its major power centres and the heart of its self-proclaimed caliphate where troops and supplies can be moved freely. The group has not been perceived as particularly strong in the area, where Al Nusra is the dominant hardline faction.

And now ISIL forces in the area find themselves locked in combat with their former allies Al Nusra while simultaneously fighting Hizbollah, which has proven extremely adept in seizing territory quickly and fighting in the rugged mountains along the border over the past month.

While Hizbollah has been playing up ISIL’s aspirations to take territory inside Lebanon, Hilal Khashan, a political science professor at the American University of Beirut, says that it is just propaganda meant to drum up support for the Iran-backed Shiite party.

According to Mr Khashan, ISIL’s real goal is to threaten the Syrian city of Qusayr and disrupt Hizbollah’s lines to the city. Hizbollah entered Syria’s civil war in 2012 to defend the regime of Syrian president Bashar al Assad. Since then, the group has spearheaded a number of major pro-regime assaults. Hizbollah helped the Syrian army capture Qusayr in June 2013.

However, the group’s presence has raised tensions in Lebanon, infuriating their domestic opponents.

“I think this was the beginning and I expect them to make more attacks,” said Mr Khashan. “The war with ISIL has just begun.”

Retired Lebanese army general Hisham Jaber said while Shiite border towns face a limited threat from ISIL and Al Nusra due to a heavy Hizbollah presence and armed and committed local populations, Christian towns were in danger.

“The Christian towns, they don’t have any real fighters. The Christian towns are counting on the Lebanese army,” he said.

The army was trying its best to protect them, but it has “limited capabilities”, he said.

As Hizbollah’s offensive inside Syria has disrupted supply lines and further isolated Al Nusra and ISIL forces, Gen Jaber says the groups will either be forced to retreat deeper inside Syria or mount offensives around the Lebanese border town of Arsal to re-establish their supply lines.

But while ISIL is a threat right now, retired Lebanese army brigadier general Tannous Mouawad said the group has little chance of victory inside Lebanon as it is opposed by all the major groups in the country.

“The ISIL threat is serious to Lebanon but the Lebanese Sunni social structure is totally, strongly against ISIL,” he said.

“For Lebanon, I am confident that ISIL does not have a chance.”

foreign.desk@thenational.ae