The chief of police for Zabul province in southeastern Afghanistan, Ghulam Saki Roghlewanai, says some explosives had been placed earlier near a prison wall.
He says the explosion today was triggered by a child although it wasn't clear whether the child did it intentionally.
The police official says after the explosion two Taliban prisoners inside tried to grab the weapons of the police guards.
He says the police managed to shoot and kill the two Taliban prisoners. He says two officers were also wounded in the incident.