The Lebanese army defused a car bomb at dawn Friday in the eastern Bekaa Valley, a stronghold of the Iranian-backed Hezbollah, after giving chase to suspects, a security source said.
The car rigged with 400 kilogrammes (250 pounds) of explosives was found just three days after twin suicide bombings targeting the Iranian embassy in Beirut killed 25 people, and as Lebanon marked its national day.
The army, on alert since Tuesday's attack outside the Iranian embassy, had spotted the suspect vehicle earlier, state media said.
Troops gave chase to the car and exchanged fire with the passengers but it got away, the official National News Agency said.
The army eventually found the vehicle abandoned on a road between the villages of Makneh and Yunin with its tyres burst, the news agency said.
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The identity of the passengers was not immediately known nor was it clear where they had planned to blow up the vehicle.
The incident came as Lebanon marked the 70th anniversary of its independence from French colonial rule.
The 32-month conflict in neighbouring Syria has stirred sectarian tensions in Lebanon where many Sunnis back the armed uprising and are opposed to Hezbollah's intervention since April alongside President Bashar al-Assad's forces.
On Thursday, Lebanese President Michel Sleiman warned against involvement in the Syria conflict, saying it was endangering the peace and unity of Lebanon, in a clear reference to Hezbollah.
"We cannot talk of independence if parties or groups ignore the state... and decide to cross the border and get involved in an armed conflict on the soil of a brother country and endanger national unity and civil peace," Sleiman said.
In October, the army defused a car bomb in south Beirut, another Hezbollah stronghold, weeks after it was hit by two bombings.