Gunmen killed nine U.N. Bangladeshi peacekeeping troops in an ambush in northeastern Congo, the deadliest assault ever on the 6-year-old mission trying to shepherd the nation out of the chaos of a civil war that left some 3 million dead. The attack occurred Friday near the town of Kafe as 21 Bangladeshi peacekeepers were patrolling in the area of a camp housing families displaced by persistent fighting in Congo's lawless Ituri province, U.N. spokesman Mamadou Bah said. The assailants are believed to have been hiding in the thick grass along the roadside and pounced on the patrol as it drove past, said Col. Dominique Demange, head of U.N. troops in Congo. The gunmen escaped before peacekeepers could fully react. The United Nations sent an attack helicopter and a rapid reaction force, but bad weather limited their effectiveness, Demange said. U.N. Secretary-General Kofi Annan condemned the "reprehensible and criminal attack" and called on Congo's transitional government to bring the killers to justice, his spokesman Fred Eckhard said in New York. Annan said the Congo peacekeeping mission would not be deterred from carrying out its mandate. Bangladeshi President Iajuddin Ahmed and Prime Minister Khaleda Zia issued messages of "condolence and profound sorrow." The peacekeepers had arrived in Kafe, 20 miles (32 kilometers) northwest of the provincial capital of Bunia, on Jan. 23 to help secure and feed and administer medicine to people who'd fled the fighting.