He added that the assault on Uvira, in South Kivu province, "flies in the face of all the negotiations that are under way". Burundi has been a natural ally of DR Congo for years because of its enmity with Rwanda. Based in South Kivu, it is mainly made up of Tutsis - and has attacked Burundi in the past. Shortly afterwards the rebels captured the next big city in eastern DR Congo, Bukavu, capital of South Kivu. Prof Stearns said he could not see this happening either while Rwandan troops remained in eastern DR Congo, and fighting continued.