Pakistani forces on Saturday destroyed a headquarters of an Islamic militant group in the Khyber tribal area bordering Afghanistan, officials said. Helicopter gunships, paramilitary troops and artillery units carried out the attack on a Lashkar-e-Islam headquarters in the Tirrah valley, a security official in Peshawar said. Pakistani forces have been fighting an offensive in the area after a suicide bomber blew himself up inside a police barracks near the Torkham border crossing between the two countries on August 28, killing 22 policemen. "Today (Saturday) the security forces destroyed the hideouts and a training centre of the Lashkar-e-Islam in Tirrah valley, heavy casualties of militants are expected," said a Frontier Corps statement. Security forces on Thursday destroyed the vacated house of Mangal Bagh, hardline chief of the group. He had already escaped to the mountains, officials said. Bagh is accused by officials of running torture centres and private jails and running a Taliban-style system in some parts of Khyber tribal district. "So far, 57 militants have been killed during six days of operations, five security men were wounded," Tariq Hayat, the top administrator of Khyber told reporters on Saturday. The operation would continue until the militants are completely eliminated, he added. Khyber is on the main land route through Pakistan into Afghanistan, where international forces are battling a Taliban insurgency.