A bomb blast ripped through a bus carrying security personnel in Quetta city of southwest Pakistan on Thursday, killing 12 people and injuring more than 20, police officials said.
The bomb, planted in an auto-rickshaw, went off as the bus carrying Balochistan Constabulary personnel was passing through the Bhosa Mandi area on the outskirts of the city Thursday morning.
Deputy inspector general of police Fayyaz Ahmed Sumbal said 10 security personnel and two civilians were killed.
The injured were taken to the nearby Civil Hospital.
Those with serious injuries were later shifted to a military hospital. Officials said five of the wounded were in a critical condition.
Police officials said the bomb was detonated by remote control while the bus was passing through the area.
Members of the bomb disposal squad said an estimated 100kg of explosives were used in the attack.
Footage on television showed that the bus was destroyed by the blast. Debris lay scattered over a wide area.
Local residents and rescue teams rushed the dead and injured to hospital.
Law enforcement agencies, including the Frontier Corps and police, cordoned off the area and launched a search operation. No group claimed responsibility for the attack.