Syed Imtiaz Shah, the local police chief, says the bombing of the center in Quetta on Wednesday killed 12 police, a soldier and a civilian. Another 23 people were wounded.
Police official Shahzada Farhat said the attack appeared to be a suicide bombing, but investigations are ongoing.
Shah says the bomb exploded outside the polio center shortly before vaccination teams were due to be dispatched to local neighborhoods as part of a three-day immunization campaign. Polio workers in Pakistan have been the victims of several terrorist attacks in recent years.
Related story
'Special Polio Vaccination Drive' to take place in 15 districts
