At least four Pakistani soldiers were killed in an attack by suspected militants in the country\'s restive Khyber tribal region bordering Afghanistan on Thursday, state television reported. PTV reported that 8 more soldiers were injured in an attack at a security checkpost in Bara area of Khyber agency near the Afghan border. The security forces returned fire at the direction of the attack and injured two militants, the report said. The forces also launched a search operation after the attack and shelled hideouts of the militants. Locals said that the militants used heavy weapons including rockets, hand grenades and automatic guns to hit the roadside checkpost of the security forces. No group has claimed responsibility for the attack. It is the second attack on security forces in Khyber agency in four days. On Monday, clashes between the militants and the Pakistani forces left 9 soldiers and 16 militants dead after the heavily- armed gunmen ambushed troops during a search operation. Militants have recently stepped up attacks in recent weeks on security forces in Khyber agency, the main supply route for NATO forces in neighbouring Afghanistan. Militants routinely attack NATO supply trucks in the region. Tehrik-e-Taliban Pakistan and another militant group Lashkar-e- Islam are active in the area. The security forces have launched several operations in Khyber agency and cleared most of the areas of the militants but they are still active in several areas.