Lebanese security forces killed two Syrians and arrested three people in an operation targeting ISIL-linked militants in the north-eastern border town of Arsal.
Yasser Al Ghawi, believed to be behind multiple bomb attacks in Ras Baalbek near the Syrian border in May, and Atef Al Jaroudi were killed while trying to resist arrest, said the Lebanese army on Tuesday. A Lebanese national suspected of weapons-smuggling was also arrested.
The army seized seven explosive devices, an explosive belt, hand grenades, and 50 kilogrammes of material used to make explosives.
It said a major security operation against suspected militants in Arsal is under way. In late June, authorities arrested nearly 400 people in a raid at refugee camps in the area.
A Lebanese military prosecutor ordered forensics last week to examine the bodies of four Syrian detainees who died in army custody, after rights groups called for an investigation.
The Lebanese army says it regularly stages operations targeting ISIL and former Al Qaeda-linked militants in the hills around the border.
Some attacks in Lebanon have been linked to the six-year war in neighbouring Syria, where Lebanese Shiite group Hizbollah is fighting in support of president Bashar Al Assad.
There are more than one million registered refugees in Lebanon fleeing the civil war in Syria.
* Additional reporting by Reuters