Hezbollah chief Hassan Nasrallah said that ISIS holds around 296 square kilometres (115 square miles) on both sides of the border.
Beirut: The Lebanese army announced Saturday the start of an offensive against the Islamic State (ISIS) group close to the Syrian border in the east of the country, where jihadists have been operating for several years.
"In the name of Lebanon, in the name of kidnapped Lebanese soldiers, in the name of martyrs of the army, I announce that operation 'Dawn of Jurud' has started," army chief General Joseph Aoun said, referring to the mountainous Jurud Arsal border region.
Hezbollah, which provides military support to Bashar al-Assad's regime in Syria, launched last month an offensive to eliminate Syrian rebels as well as all jihadists formerly linked to Al-Qaeda from the region.
After six days of fighting, a ceasefire deal between Hezbollah and fighters from Al-Qaeda's former Syrian affiliate, previously known as the Al-Nusra Front, was announced.
Nearly 8,000 refugees and jihadists from Al-Qaeda's former Syrian branch were bused back to Syria following the deal and on Monday the last Syrian rebels were evacuated from the region.
The army is now launching an offensive against the ISIS fighters still operating in the area.
Jurud Arsal had been used for years as a hideout by Syrian anti-regime militants but was also home to an unknown number of refugees seeking shelter from Syria's six-year war.
Hezbollah chief Hassan Nasrallah said that IS holds around 296 square kilometres (115 square miles) on both sides of the border, of which around 140 square kilometres are in eastern Lebanon.