The clashes with small arms and heavy weapons broke out in the Abu Slim area near central Tripoli, an AFP journalist and witnesses said.
Gunfire from heavy weapons could be heard in several areas of the centre, while plumes of smoke could be seen rising into the sky above Abu Slim, an AFP journalist at the scene said.
"It's a war here," Meftah, a resident of the area,told AFP.
Rebels from Zintan first entered Tripoli in August 2011, when they helped to drive forces loyal to former dictator Muammar Gaddafi out of the capital.
More From This Section
Yesterday, a group of gunmen from Zintan attacked the headquarters of the petrol installations guard, for reasons that are still unclear, before other groups of ex-rebels intervened with force to stop them.
Members of the country's highest political authority, the General National Congress, said in a statement today that clashes the night before in the Tripoli suburb of Salaheddin had killed five people.
The authorities, who are struggling to form a professional army and police, regularly use former rebels to secure the borders or to intervene in tribal conflicts.