A senior security official said on Saturday that 40 people have been killed and more than 70 wounded in the fighting erupted after gunmen fired on a procession in Parachinar, about 250km south-west of Peshawar.
Interior Minister Aftab Ahmed Khan Sherpao has said death toll could reach at 50. Authorities on Friday imposed a curfew and troops started patrolling to restore order.
Clashes started when a group of people took out a procession in Parachinar and chanted slogans against their rivals, according to a locals.
Locals said that firing stopped on Saturday in the afternoon after army took complete control of the city but firing started in Pewar, Balash Khel, Sadda, Bashra, Mali Khel, Karman and Para Chamkani.
Eye witnesses said that both sides are using mortars, rockets and missiles as well as automatic guns.
Secretary Security for tribal region Sahibzada Arif had confirmed the deaths of 40 people but locals said that casualties may increase as fighting has spread outside the city.
Authorities have ordered shoot-at-sight if anyone violate curfew. Army contingents are patrolling in Parachinar and the situation is under controlled in the city. '