At least two people were killed and 10 wounded when clashes broke out between armed members of the militant group Hezbollah and tribal members south of Beirut on Thursday, local media reported.
The clashes in Khaldeh, south of the Lebanese capital, reportedly erupted after a row over banners that had been hung.
The National News Agency said the two dead were a Lebanese and a Syrian citizen; the three wounded were members of the same family.
Heavy automatic weapons fire could be heard in videos posted to social media.
The clashes took place around the motorway that links Beirut with the country’s south.
The Lebanese army was sent to the area, made four arrests and sealed off the motorway.
"Four people have been arrested in Khaldeh, including two Syrians, and the rest of those involved are being pursued," the army said.
It said reinforcements were being sent to the area.
The fighting lasted nearly three hours and a nearby building was torched.
Lebanese President Michel Aoun called different political factions to try to calm the situation.
Last week, a brief clash broke out in the same area when Hezbollah supporters tried to raise a poster of Salim Ayyash, a Hezbollah member charged by a UN-backed tribunal of involvement in the assassination of former Lebanese Prime Minister Rafik Hariri in a huge suicide truck bombing in Beirut 15 years ago.
In its verdict August 18, the Special Tribunal for Lebanon convicted Ayyash and acquitted three others of involvement in the assassination, which sent shock waves through the Middle East.
The country is still reeling from devastating explosion that destroyed Beirut port on August 4.
It is also suffering from a crippling economic crisis.
Hezbollah's leader Hassan Nasrallah warned of a risk of civil war in Lebanon after the blast.