FISTON MAHAMBA ARMED men killed at least a dozen people and kidnapped several in northeast Democratic Republic of Congo on Sunday night, authorities said, the latest in a string of attacks they have blamed on Ugandan Islamist rebels. Violence attributed to the Allied Democratic Forces (ADF), a Ugandan armed group active in eastern Congo since the 1990s, has surged since the army began a counter-insurgency campaign against them late last year. Armed men attacked the city of Mbau in Beni territory, North Kivu province, near the Ugandan border, killing and kidnapping people and burning houses before fleeing into the bush,…