Pakistan’s Interior Minister has said an operation against militants on the Afghan border is imminent.The statement follows Saturday’s attack on the army headquarters. In a gunbattle at a main gate, attackers wearing army uniforms took hostages and killed six soldiers, including a brigadier and a lieutenant colonel. Pakistani commandos have now rescued 39 of the hostages but the attack prompted US Secretary of State, Hillary Clinton, to say militants in Pakistan were increasingly threatening the authority of the state. The attack came as the military prepared for an offensive against the militants in their stronghold of South Waziristan on the Afghan border. The army has been preparing for a major operation in the area since it successfully cleared the Swat valley of militants in September. In March, militants pushed to within 100 km of Islamabad, sparking grave concern for Pakistan’s stability and fears for the safety of its nuclear weapons.