At least four people including a woman and three children were killed and five others, including two cops, sustained injuries when an improvised explosive device (IED) went off near police station in Umerzai area on Monday. Police said that unknown miscreants planted IED near the police station in Umerzai area which went off prematurely killing a woman and three children and injured five others including two police personnel. The injured were shifted to hospital for treatment. The bomb explosion partially destroyed the boundary wall of the police station which was the main target of the blast and also a mosque was partially damaged. Sources said that it was the first terror attack on a police station after the killing of Osama Bin Laden.