Hutu Rwanda, this led to the "Social revolution" and Hutu violence against Tutsis. Tens of thousands of Tutsis were killed and many others fled to neighboring countries, such as Burundi, Uganda and expanding the Banyamulenge Tutsi ethnic group in the South Kivu region of the Belgian Congo. Later, exiled Tutsis from Burundi invaded Rwanda, prompting Rwanda to close its border with Burundi. In Burundi, a campaign of genocide was conducted against Hutu population in 1972, and an estimated 100,000 Hutus died. In 1993, Burundi's first democratically elected president, Melchior Ndadaye, who was Hutu, was believed to be assassinated by Tutsi officers,
Rwanda Nziza under the presidencies of Gregoire Kayibanda and Juvénal Habyarimana, were marked by continued cycles of violence, culminating in the 1990s with the launch of the Rwandan Civil War by exiled Tutsi led by Paul Kagame, the assassination of President Habyarimana, and the 1994 Rwandan Genocide, in which between 500,000 and 1,000,000 Tutsi and politically moderate Hutu were killed by Hutu extremists, on the orders of the interim government, in the space of just 100 days. The genocide was ended when Kagame's rebel army took control of the country in July 1994. A period of reconciliation began, as a unity government