The origin is said to be that a militia leader was arrested and taken into custody by a rival group. He is said to have been released later, reports say al-Jazeera.
The Ministry of Health has appealed to the rival groups to allow ambulances into the fighting areas and to allow blood transport to nearby hospitals. Over 30 people have been injured, a hospital source told AFP.
Libya has been torn apart by conflict since dictator Muammar Gaddafi was overthrown and killed in 2011.