Gunmen on motorcycles attacked a bus in southwestern Pakistan near the Iranian border on Friday, killing 18 people and wounding two, Pakistani police said, according to Reuters.

The attack occurred when the bus, which was heading for Iran, stopped at a roadside shop in the Kech area of Baluchistan province, the police said. They said six gunmen were involved.

No further details were immediately available.

Several militant groups are active in Baluchistan, Pakistan's biggest but poorest province.

Much of the violence in the past has been blamed on ethnic Baluch separatists, who are fighting a protracted insurgency, demanding more autonomy and control over the natural resources of the province.

Pro-Taliban militants are active in the province, which borders both Afghanistan and Iran.

Sunni Muslim militants also regularly carry out attacks on Baluchistan's Shi'ite minority. They have stepped up attacks in recent months.