Israeli Air Force planes attacked a target along the Syrian-Lebanese border overnight, Western sources were quoted in saying.
Lebanese sources reported heavy Israeli Air Force activity overnight but later the Lebanese state run news agency NNA media denied reports of an attack.
Reports said Israel had attacked a weapons convoy. Israeli television said the convoy might have been moving anti-aircraft rockets from Syria to Lebanon.
Syria has been described as a "chemical weapons superpower." Israel has long warned that as the regime in Damascus disintegrates, Syrian President Bashar Assad could try to transfer its chemicals weapons stockpile to Hezbollah in Lebanon.
Israel declined to comment on the reports but earlier this week warned it might intervene if Syria seemed to be losing control of its chemical weapons.
Earlier Israel moved Iron Dome anti-missile batteries to Haifa in northern Israel.