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,
History of Rwanda dominated by the majority Hutu under President Grégoire Kayibanda. Unsettled ethnic and political tensions were worsened when Juvénal Habyarimana, who was also Hutu, seized power in 1973. In 1990, the Rwandan Patriotic Front (RPF), a rebel group composed of 10,000 Tutsi refugees from previous decades of unrest, invaded the country, starting the Rwandan Civil War. The war ground on, worsening ethnic tensions, as the Hutu feared losing their gains. The assassination of Habyarimana was the catalyst for the eruption of the 1994 genocide, in which hundreds of thousands of Tutsis and some moderate Hutus were killed. The Tutsi RPF conquered