UPPER DIR - At least 11 persons including four schoolgirls were killed and over a dozen injured near Dir when some unknown militants attacked a police vehicle with an Improvised Explosive Device (IED) on Thursday, officials said on Thursday. Three policemen, four prisoners and four minor school-going girls were among the killed persons, they said. A police vehicle was going from Dir town to Timergara Jail after producing under-trial prisoners in district courts. When the vehicle reached near Meetha Pani (Sweet Water), around two kilometres away from Dir, an IED, planted by unknown militants, hit the police vehicle, killing two policemen and four prisoners on the spot. A school van, following the police vehicle closely, was also hit by the IED and as a result four schoolgirls were killed. The officials informed that the killed persons were identified as Khudadad, Noor Nawab, Rizwana, Farhana, Basila, Sunbal, Badsha Rehman, Tazamin Khan, Sajidullah and Jehanzeb. The officials also said that more than a dozen including several schoolgirls sustained injuries in the incident. The condition of the six injured persons is reported precarious and they have referred to a Peshawar hospital. So far no one has claimed responsibility for the attack. The officials said that investigation was in progress.