Eight people were killed and many wounded on Monday when Lebanon's army targeted militant positions along the eastern border with war-torn Syria, security sources told AFP.

"The Lebanese army targeted militants on the border" with Syria, a security source said.

A separate security source said a "helicopter fired a missile at takfiri (extremist Sunni) positions in Wadi Hmeid", on the eastern outskirts of the border town of Arsal.

He said eight people were killed and "a large number" of others wounded, but he could not say if the dead were militants or civilians.

The Lebanese army has battled militants along the border with Syria for over a year in sometimes bloody clashes.

The border area is also home to informal Syrian refugee camps largely beyond the reach of authorities or aid agencies.

Lebanon's National News Agency reported the incident as an "explosion in the Syrian refugee camps that killed four people and injured others", but gave no further details.

Security sources denied the camps were hit.

Arsal, a largely Sunni town, was the site of fierce fighting in August 2014 between Lebanese security forces and fighters from Al-Qaeda's Syria affiliate and ISIS militant group.

As they withdrew from Arsal, the militants took dozens of Lebanese security forces hostage and still hold them in the hilly terrain on the town's outskirts.

Another security source told AFP that earlier on Monday a mortar shell crashed outside a Lebanese army border post on the outskirts of Arsal, without causing any casualties.