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,
Burundi some Hutu felt this was unjust and ethnic tensions were further increased. In October 1965, an attempted coup d'état led by the Hutu-dominated police was carried out but failed. The Tutsi dominated army, then led by Tutsi officer Captain Michel Micombero purged Hutu from their ranks and carried out reprisal attacks which ultimately claimed the lives of up to 5,000 people in a precursor to the 1972 Burundian Genocide. King Mwambutsa, who had fled the country during the October coup of 1965, was deposed by a coup in July 1966 and his teenage son, Prince Ntare V, claimed the throne.