The army said it called in bomb disposal experts after spotting a suspicious vehicle in the Maamura area of Beirut's southern suburbs on Monday afternoon.
"The vehicle turned out to be rigged with explosives," it said, adding that the military experts were defusing it.
Lebanese army troops deployed in Hezbollah's southern Beirut suburbs in September, taking over checkpoints in a deal struck with the powerful Hezbollah resistance group after two massive bombings since July.
The security points were established after car bombings in the southern suburbs that killed 27 people on August 15 and wounded more than 50 on July 9.
Hezbollah Secretary General Hassan Nasrallah has said that a probe into the August bombing showed Salafi extremists affiliated with the Syrian foreign backed militant groups were behind it.
Lebanon is sharply divided over the raging war in neighboring Syria, with Hezbollah and its allies backing regional Resistance course as well as the legal government of President Bashar al-Assad.
NJF/NJF