The incident took place in the Hazar Ganji area on the outskirts of Quetta

"A bus carrying Shia Muslims was coming to Quetta from Iran when a car bomb exploded near it, killing 11 people including nine Shia pilgrims and two escorting policemen," senior local police official, Hamid Shakeel, told AFP.

"The victims included two female pilgrims.

"It was a remote controlled blast. The bomb was planted in a car and exploded as the bus passed by it," he said, adding that more than 20 people were injured in the attack.

He said the engine of the car was found about 50 feet away from the site of the explosion.

Two other senior police officials confirmed the explosion and casualties.

Manzoor Ahmed, a bomb disposal squad official, said the improvised explosive device weighed more than 30 kilograms.