Gunmen have attacked an Iran-bound passenger bus in south-western Pakistan, killing at least 18 people on board and injuring eight others, officials said. The incident took place in the far-flung Kechh district, some 1250 kilometers (780 miles) southwest of Quetta, the main town of Pakistan's insurgency hit Baluchistan province, close to the Iranian border, according to the BBC. A tribal police official in the area confirmed the incident and death toll. Though no group has yet claimed responsibility, such attacks are usually blamed on Baluch nationalist groups fighting for a greater provincial autonomy. Last week militant attacked a bus in Quetta, which was bringing Shi'ites pilgrims from Iran, killing 12.