Coalition forces backed by attack helicopters and gunships on Monday swept a valley in eastern Afghanistan and detained 11 suspected militants believed responsible for an roadside bombing that killed four American service members. Sunday's bombing in the Pech Valley of Kunar province was the deadliest against U.S. forces in Afghanistan in a month. It came on the same day that two suicide attackers in Kabul narrowly missed the chief of Afghanistan's upper house of parliament but killed themselves and two bystanders.The U.S. military said in a statement that Marines and soldiers backed by artillery, attack helicopters and AC-130 gunship planes swept the Pech valley after encountering small-arms fire and rocket-propelled grenades. Abdul Ghaffar Khan, chief of police in Kunar province, said Afghan police and American troops had searched mountains near Sunday's attack in which a homemade explosive hit a U.S. armored vehicle driving in a convoy. That road remained blocked to normal traffic, he said. "The coalition's response has resulted in the detention of 11 insurgents believed responsible" for Sunday's attack, the U.S. statement said, without identifying the detainees.