The Lebanese army intercepted a car packed with explosives near the border with Syria on Sunday, four days after two car bombs were defused elsewhere in the country, l'Agence France Presse reported.
State news agency NNA said the car had entered Lebanon from the embattled Qalamun region across the border and was stopped at an army checkpoint when soldiers became suspicious.
A security source told AFP soldiers opened fire towards the vehicle, prompting the passengers to flee.
The car was rigged with 200 kilos (440 pounds) of explosives which were to be triggered by mobile phones, the source said.
In a statement, the army confirmed the incident, saying the vehicle contained 240 kilos of Semtex explosives as well as artillery shells.
It said the Semtex and other explosives in the car were connected to a detonation cord of 200 metres (yards) and a timing system involving two cell phones and a battery.
It added that drugs were also found in the car, without providing details.
The NNA said the car had come from the Qalamun region "and was heading towards Beirut".
It identified the vehicle as a four-wheel drive and said it was seized along the Shoaybe-Ham highway in eastern Lebanon.
On Wednesday, the army said it defused two car bombs, one in Beirut and a second in eastern Lebanon which it said had come from Yabrud, a bastion of Syrian rebels in the Qalamun mountains.
Lebanon has seen a string of deadly attacks, including car bombs, linked to Syria's war, claimed by Al-Qaeda-linked groups.
Although officially neutral in Syria's conflict, Lebanon is deeply divided over the Sunni-led rebellion against President Bashar al-Assad, whose troops are backed by fighters from the Shiite movement Hezbollah.