"Twelve people were injured in a suicide attack at an army checkpoint," the National Information Agency (ANI) reported.
"It was a car bomb and there is a strong possibility that it was a suicide attack," a security source told AFP.
There was no immediate word on any victims of the blast, but ambulances could be seen transporting some of the wounded.
An AFP photographer saw several cars on fire at the scene and other damage.
Firefighters were tackling the blaze.
A witness told Lebanese television that he saw a white Mercedes car travelling fast on the wrong side of the road before exploding.
"Terrorism seeks to undermine our unity," Hezbollah deputy Ali Ammar said.
"The Sunni extremists, after their defeat in Syria, are trying to open new fronts and what we are seeing in Iraq is not too much different from what's happening in our country, but here the circumstances don't allow them to operate in the same fashion," he added.
The car bombing came three days after a suicide attack in the east of the country which left one person dead and 30 wounded.
The area of south Beirut, a stronghold of Lebanon's Shiite movement Hezbollah, has been the target of attacks for many months.
Most of these were claimed by Sunni extremists who blamed the Shiite movement for sending thousands of fighters into Syria to support President Bashar al-Assad's regime in neighbouring Syria.
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"It was a car bomb and there is a strong possibility that it was a suicide attack," a security source told AFP.
There was no immediate word on any victims of the blast, but ambulances could be seen transporting some of the wounded.
An AFP photographer saw several cars on fire at the scene and other damage.
Firefighters were tackling the blaze.
A witness told Lebanese television that he saw a white Mercedes car travelling fast on the wrong side of the road before exploding.
"Terrorism seeks to undermine our unity," Hezbollah deputy Ali Ammar said.
"The Sunni extremists, after their defeat in Syria, are trying to open new fronts and what we are seeing in Iraq is not too much different from what's happening in our country, but here the circumstances don't allow them to operate in the same fashion," he added.
The car bombing came three days after a suicide attack in the east of the country which left one person dead and 30 wounded.
The area of south Beirut, a stronghold of Lebanon's Shiite movement Hezbollah, has been the target of attacks for many months.
Most of these were claimed by Sunni extremists who blamed the Shiite movement for sending thousands of fighters into Syria to support President Bashar al-Assad's regime in neighbouring Syria.
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