The ceasefire comes a week after Hezbollah launched an offensive against the militants in the Arsal border region
Fighting between Lebanon's Hezbollah movement and a former al-Qaeda affiliate on the Syria-Lebanon border halted Thursday after a ceasefire was reached, Lebanese media and Hezbollah outlets reported.
The ceasefire comes a week after the powerful Shia militant group launched an offensive against the militants in the mountainous Jurud Arsal border region.
Hezbollah's "War Media" outlet said "a ceasefire that began at 6:00 am (0300 GMT) is in effect on all the front in Jurud Arsal."
Lebanon's official National News Agency said the ceasefire was part of a deal brokered by the country's general security agency chief Major General Abbas Ibrahim.
Under the deal, remaining fighters from the former al-Qaeda affiliate once known as Al-Nusra Front will withdraw from the region.
Al-Nusra Front was previously al-Qaeda's Syrian affiliate, before renouncing that status last year and rebranding itself Fateh al-Sham Front.
"The Al-Nusra fighters and their families will go to Idlib," a province in northwestern Syria largely under the control of the militants, NNA said.
It said Ibrahim was expected to release a statement on the deal later on Thursday.
In a speech on Wednesday, Hezbollah chief Hassan Nasrallah said "serious" negotiations were underway to secure the withdrawal of Al-Nusra militants.
"There are two paths: the battlefield and the negotiations. Both are open," he said.
He had said his fighters were on the cusp of "a great military victory", and had surrounded the remaining Al-Nusra fighters in a small pocket of territory.
Security in Jurud Arsal has been a concern for many years.
The barren and mountainous border area has served as a hideout for militants, who in 2014 clashed with Lebanese security forces in the area.
Tens of thousands of Syrian refugees live in the town of Arsal, adjacent to the border region, while an unknown number are also thought to have been sheltering in the surrounding mountains.
Lebanon's army has not officially declared its participation in the operation, but has shelled "terrorists" in the area.
It has also been involved in operations to transport civilians out of the battle zone and into the town of Arsal.
In his speech on Wednesday, Nasrallah said his fighters were willing to hand over the territory they have secured to Lebanese troops.
But the group's fighters told journalists in Jurud Arsal on Wednesday that the next phase of the battle to secure the region was still ahead.
They said Islamic State group fighters still hold parts of Jurud Arsal and the area around two border towns, but anticipated an easy victory.
"It won't be a difficult task. Its fighters are only a few hundred and spread out in this vast territory," one commander said confidently.