The fighting pitted the African-origin Tabu tribe against the Arab-origin Awlad Soliman tribe in the city of Sabha, some 650 kilometres south of Tripoli. The ministry said the fighting, which began Friday, also wounded 65 people.
A local leader said yesterday that the fighting was sparked by the killing of a guard of the city's military leader, a member of the Awlad Soliman tribe, in retaliation for 2012 killings of dozens of Tabu men.
The downfall of Gadhafi and his allied tribes in the area have seen the Tabu gained control over the borders. Meanwhile, gunmen killed Hassan Drouai, the deputy minister, in coastal city of Sirte late yesterday, a security official said. Drouai was shot to death near a central market, said the official, who spoke on condition of anonymity because he was not authorised to brief reporters.
Libya's current government has failed to rein in hundreds of militias born out of former rebel brigades including those led by extremist Islamic commanders.