Authorities in Pakistan's south-west Balochistan province now say more than 20 died in Thursday's clashes between soldiers and rebel tribesmen.
Eight soldiers and about 15 tribesmen were killed in fighting around Dera Bugti, a spokesman for the paramilitary Frontier Corps said.
However, a tribal chief said the army had killed more than 50 locals.
The tribesmen demand greater political and economic rights. They also blame army members for raping a local doctor.
Separately on Friday a bomb exploded in a toilet of a train near the provincial capital of Balochistan, Quetta, killing one person and injuring five, police said.
The paramilitary spokesman said that in addition to the eight Frontier Corps troops killed in the clashes, 23 were injured in the fighting.
Forty troops whose convoy was besieged by more than 100 tribesmen had been freed after a ceasefire was arranged, he said.
Dera Bugti is home to one of the tribal chiefs pressing demands for greater political autonomy and a greater share of the revenue from the province's gas reserves.
Balochistan has been tense for several months
The chief, Nawab Akbar Bugti, said his home had been shelled and that more than 50 tribal men, women and children, many of them ethnic Hindus, had been killed.
The Frontier Corps spokesman said that figure was exaggerated.
The clashes are the most serious since eight people were killed in several days of fighting in and around strategically important gas fields in the area in January.
Those clashes were sparked by the alleged rape of the doctor. Renegade tribesmen rained rockets on security forces guarding the gas installation where they said the attack took place.
Since then the army has moved extra forces into the area.
In the past two months tribal fighters have staged small-scale but almost daily attacks, hitting the security forces and the province's rail, power and communications infrastructure.
Tribal leaders fear a big military operation to crush their well-armed forces may be imminent.
The army, however, says there are no such plans at present.
Friday's train bombing took place when the Chiltan Express had stopped in the town of Mach, near Quetta, on its journey from Lahore.
Officials said no one had yet claimed they carried out the attack.