Gunmen riding on two motorcycles opened fire on a bus at a small fuel station in southwest Pakistan on Friday, igniting a massive blaze and leaving 18 dead, a Pakistani official said.

Abdul Mansoor Kakar said all 16 people on the bus, including eight women and three children, were killed and the bodies badly burned. The vehicle had been parked next to fuel drums that ignited during the attack, starting a fire that engulfed the bus and killed two in a nearby car.

The attack took place in the town of Khuzdar in the province of Baluchistan.

No one claimed responsibility and the motive of the attack was unclear, Kakar said, adding that the incident was under investigation but no arrests were made.

Khuzdar is located 300 kilometers (180 miles) south of Quetta, the capital of Baluchistan province. The region has experienced a decades-long insurgency by nationalists who demand greater autonomy and a larger share of the province's natural resources.

The province is also thought to be home to many Afghan Taliban militants.