Pakistan authorities say gunmen have opened fire on a bus carrying Shi'ite Muslim pilgrims in the country's southwest, killing 26 pilgrims.

Officials in Pakistan's Baluchistan province said the attack occurred Tuesday about 50 kilometers outside Quetta as the bus was traveling to Iran. They say the gunmen stopped the bus and then opened fire.

While no one has claimed responsibility, Pakistan has a history of sectarian violence. The country has a Sunni Muslim majority, and although most Sunnis and Shi'ites coexist peacefully, extremists often target members of each community.

In other violence, Taliban gunmen attacked a Pakistani military checkpoint in the country's northwestern tribal belt, leaving at least 19 people dead.

Officials said the militants launched the attack in the Dabori region of Orakzai tribal agency, killing at least one soldier and wounding five others.

Security forces were able to kill more than 18 militants in the ensuing gunbattle. Pakistani helicopter gunships also were involved in the fight.

There was no independent confirmation of the death toll. The area is largely shut off from journalists and aid workers.

Last year, the Pakistani military launched an operation against the Taliban in Orakzai. Pakistan's semi-autonomous and remote tribal region near the Afghan border has been the center of militant activity. Domestic and Afghan Taliban elements are located there as well as al-Qaida operatives and other foreign fighters.