Pakistani security forces killed 33 militants on Sunday as part of a week-old campaign in the Khyber Pass, the main land route used to supply Western and Afghan forces in Afghanistan. Based on official statements nearly 120 insurgents have been killed in the past week, but independent casualty estimates are unavailable. The military swung into action in Khyber, one of Pakistan's seven semi-autonomous tribal regions, days after a suicide bomber killed 22 border guards. Aside from militant factions based in Khyber, other fighters fled there to escape an assault further east on the Taliban stronghold in the Swat valley, where the army went on the offensive in late April. Truck convoys carrying supplies to U.S., NATO and Afghan forces regularly come under attack as they trundle through the pass that links Pakistan and Afghanistan. During Sunday's fighting, troops cleared two militant compounds and demolished 17 houses said to belong to insurgents. "Security forces targeted two militant centers. They destroyed them and killed 33 militants in the operation," a Frontier Corps spokesman said in a statement. The show of force in Swat and elsewhere has helped allay fears among Western allies that the nuclear-armed Muslim nation was failing to confront spreading Islamist militancy.