Lebanon's army found anti-aircraft missiles among with a cache of weapons in an area abandoned by Islamic State militants, it said on Monday.
The arms cache also included mortars, medium and heavy machine guns, assault rifles, grenades, anti-tank weapons, anti-personnel mines, improvised explosive devices and ammunition.
On Saturday Lebanon's army began an operation to dislodge Islamic State from its small enclave in the mountains straddling the border with Syria.
The Syrian army and Lebanon's Shi'ite Hezbollah group are conducting a simultaneous but separate operation against the same pocket from inside Syria.
A Hezbollah offensive last month forced militants from the Nusra Front group, formerly al Qaeda's official Syrian branch, to quit an adjacent enclave on the border for a rebel-held part of Syria.
On Friday, the Lebanese army said it had discovered surface-to-air missiles in a weapons cache left by the Nusra militants in an area captured by Hezbollah and then taken over by the army.