17 people have been killed in fighting between Sunni and Shia Muslims over a shrine in Pakistan's North-West Frontier Province
The sides exchanged rocket and mortar fire in a dispute over ownership of the shrine to 18th Century figure Syed Amir Anwar Shah in Orakzai tribal region.
The violence began four days ago when clerics from the two sects tried to occupy the shrine.
The latest violence has brought the official death toll to 23.
However, tribesmen in the area claim that the number of dead is higher.
There were also reports that armed groups from neighbouring tribal regions were arriving in Orakzai to aid Sunni and Shia fighters.
The political administrator for Orakzai, Dr Sher Mahsud, told reporters on Friday that the government had sent Frontier Corps forces to the area to prevent further fighting.
Tribal elders and religious scholars from adjoining regions were being brought in to mediate between the feuding tribes, said Dr Mahsud.
Violence blamed on militants from Pakistan's Sunni and Shia communities has cost the lives of thousands of people over the past two decades.
Sunni Muslims account for around 80% of Pakistan's 160m people and are the dominant group in the tribal areas, although Orakzai has a significant Shia population.
The semi-autonomous tribal regions, which border Afghanistan, are heavily militarised, a legacy of the mujahideen war fought against the Soviet occupation of Afghanistan in the 1980s.
At Least 13 Killed in Pakistan Violence