The ceasefire ends fighting between the Lebanese group and Jabhat Fateh al Sham fighters in the Jurud Arsal area.
Fighting between Lebanon's Hezbollah group and a former Al Qaeda affiliate on the Syria-Lebanon border halted on Thursday after a ceasefire was reached, Lebanese media and Hezbollah outlets reported.
The ceasefire comes a week after Hezbollah launched an offensive against Jabhat Fateh al Sham militants in the mountainous Jurud Arsal border region.
The group used to be called Jabhat al Nusra and was affiliated with Al Qaeda before it joined five other groups to form Hayat Tahrir al Sham in January 2017.
Hezbollah's Al Manar TV website said that "a ceasefire that began at 6:00 am (0300 GMT) is in effect on all the front in Jurud Arsal."
Daesh to be targeted next
Security sources say some two dozen Hezbollah fighters and nearly 150 militants have been killed overall.
Hezbollah is expected to target Daesh in an adjacent area of the border zone in the next phase of its operation in the area unless the terrorist group's militants agree to withdraw.
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.
Arsal was the scene of one of the most serious spillovers of the Syrian war into Lebanon when militants briefly overran the town.
Fighters to shift to Idlib
Lebanon's official National News Agency (or NNA) 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 will withdraw from the region.
"The Al Nusra fighters and their families will go to Idlib," a province in northwestern Syria largely under the control of opposition rebels, NNA said.
Over two million people live in Idlib, which has become a refuge for many of those displaced in Syria's seven-year civil war. They include opposition fighters and their families who left areas retaken by regime forces.
Under the deal, according to the English-language Daily Star newspaper, Jabhat Fateh al Sham will release three Hezbollah fighters it captured in 2015 and 2016.
In a speech on Wednesday, Hezbollah chief Hassan Nasrallah said that "serious" negotiations were underway to secure the withdrawal of militants.
"There are two paths: the battlefield and negotiations. Both are open," he said.
Hezbollah's support for regime
Iran-backed Hezbollah has been a crucial ally of regime leader Bashar al Assad in Syria's civil war since 2012.
Hezbollah originally said it entered the conflict to protect Shia holy shrines and Lebanese villages on the border.
However, after the regime began to lose ground to the opposition and Daesh, Hezbollah began fighting on behalf of Assad. Later, the militia's intervention extended to Sunni-majority areas such as Aleppo.
Air strikes kill civilians
Meanwhile, a barrage of US-led coalition air strikes killed 29 civilians on Wednesday in Syria's Raqqa, half of which is still held by Daesh, a Britain-based war monitor said.
"At least eight children are among the dead," said Syrian Observatory for Human Rights chief Rami Abdel Rahman.
Backed by the US-led coalition, the YPG-dominated Syrian Democratic Forces (SDF) have waged a months-long offensive on Raqqa and have captured half of the city.
With Wednesday's deadly raids, at least 325 civilians, including 51 children, have died in the city since the SDF entered Raqqa less than two months ago, the Observatory said.
More than 400,000 people have lost their lives in Syria since the country collapsed into conflict after the regime repressed pro-democracy protests in March 2011. Since then the civil war has become a quagmire, not only for the people of Syria, but for the regime's foreign allies and opponents.