"More than ten people were killed today (Monday) in violent clashes between Toubu and residents of the city," chief security of the southern region of Fezzan, Abdelrahman Seif al-Nasr told AFP.
However, a former rebel says the clashes which broke out in the city center have led to the death of 15 to 20 people.
"We have taken back the offices of the military council which were seized by the Toubou. The fighting is continuing and getting worse," Former rebel Ali al-Dhib said.
He added that fighting broke out when the Toubu refused to hand over to local authorities one of their men accused of killing a man belonging to the Bussif tribe.
Toubu tribesmen have also been involved in deadly clashes with Zwai tribe in the Saharan oasis of Kufra since February 2012.
The clashes between the African country’s two ethnic communities have reportedly claimed the lives of dozens of people.