Fighting between Islamic State and the al Qaeda-linked Nusra Front spread from Syria into Lebanon's northern Bekaa Valley region on Monday, a security source and the state news agency said.
Eighteen Nusra Front members were killed and six were taken prisoner during the clashes, and 14 Islamic State members were also killed, the security source said.
The fighting began on Sunday near the Syrian town of Jrajeer in the Qalamoun mountains near the Syrian-Lebanese border, before spreading toward the Lebanese towns of Ras Baalbek and Arsal, the source said.
Lebanon's National News Agency reported that Nusra Front had fought on Sunday to regain some positions it lost to Islamic State. In the fighting it said 10 Nusra Front fighters and eight Islamic State militants had died.