The attackers surrounded the buses in Baluchistan and two gunmen entered each vehicle to check the identities of passengers, said Abdul Waheed, deputy commissioner of Bolan district, where the attack took place. While they were doing this, a paramilitary soldier tried to sneak into the area but was killed by the gunmen.
The attackers took 22 passengers with them, including nine tribal policemen, but they dropped the officers off a few miles away because they were locals, and continued with the remaining 13 hostages. Police found the bodies of the 13 hostages in a ravine near the town of Machh.
The motive for the attack is unclear as no one has claimed responsibility, but suspicion could fall on separatists who have been waging a low-level insurgency in south-west Baluchistan province for decades.
The buses were headed to central Punjab province, and the separatists have a history of attacking Punjabis who they view as outsiders encroaching on their independence. The province is also home to many Islamic militants who have carried out attacks in the past, especially on minority Shiite Muslims.