Lebanese Shi'ite group Hezbollah clashed with Sunni Islamist insurgents trying to capture land in a mountainous area near the border with Syria on Sunday and both sides suffered casualties, security sources said.
The insurgents, believed to be linked to Islamic State, launched a major offensive on Hezbollah-controlled areas near the Lebanese border town of Arsal, the sources said.
At least two Hezbollah fighters were killed and many of the insurgents, they added, without giving an extact figure. Violence from Syria has often spilled over into Arsal and surrounding areas, where the Lebanese army has also fought insurgents.
Fighters from Iran-backed Hezbollah have been aiding Syrian President Bashar al-Assad in the Syrian civil war, fighting groups such as Islamic State and al Qaeda's Nusra Front. Islamic State has seized tracts of land in Syria and Iraq.