Three people were shot dead and more than a dozen wounded in a confrontation between soldiers and civil rights protestors, Pakistan's army said.
Troops opened fire when a checkpoint in North Waziristan was shot at by protestors led by two members of Pakistan's national assembly, the military said.
However leaders of the Pashtun Protection Movement (PTM) said troops had instead opened fire on an unarmed crowd, wounding dozens.
The PTM movement has angered Pakistan's powerful military since it emerged last year, with its open criticism and calls to end alleged abuses against Pashtuns living in the tribal areas bordering Afghanistan.
The incident came a month after the army warned the PTM leadership that their “time is up”.
Protestors led by Mohsin Dawar and Ali Wazir, both members of parliament who helped found PTM, attacked a check post in Boyya to "exert pressure for release of a facilitator of suspected terrorists," the military said in a statement.
Troops came under direct fire, with five soldiers wounded, a statement said. They had showed “maximum restraint”, according to the military.
"In exchange of fire, three individuals who attacked the post lost their lives and 10 got injured," it added.
The statement said Mr Wazir had been arrested and Mr Dawar was at large.
Mr Dawar and Mr Wazir were planning to stage a sit-in along with PTM members to protest against the alleged abusive treatment of a Pakistani woman by the security forces, Reuters reported.
Mr Dawar told Voice of America's (VOA) Pashto language radio service, Deewa, that about 30 people were wounded in the incident, including himself, and some were seriously injured.
Dawar said the security forces tried to stop protestors going through barricades and initially shot in the air but "then opened straight fire at us. Many our of people were injured," Mr Dawar told Deewa.
Bilawal Bhutto-Zardari chairman of the Pakistan People’s Party (PPP) raised doubt over the military version of events, saying it made no sense for a member of the national assembly to attack a check post.
“ How can Mohsin Dawar attack a check post? He is an elected representative! It would not make sense for an elected representative to initiate such an attack,” he said.