At least three policemen were shot dead and six injured in an attack by militants in Pakistan's Peshawar city on Wednesday."A contingent of police was carrying out a search operation in Urmah area of Peshawar city when militants opened fire at their van," Dawn online quoted Senior Superintendent of Police (SSP) Operations Mian Saeed as saying.Saeed said three policemen were killed and six sustained injuries in the ambush.Police have cordoned off the area and a search operation is being carried out.The SSP said the assailants in the attack were wanted militants.