In 1959, following a decade of increasing tension between the Tutsi and the Hutu, a social revolution took place in Rwanda. Hutu activists began killing Tutsi, overturning the centuries-old Tutsi dominance amongst the Banyarwanda. The Belgians suddenly changed allegiance, becoming pro-Hutu, and the Rwandan monarchy was abolished in 1962 following a referendum. Rwanda then gained independence as a republic, under Hutu leadership. As the revolution progressed, Tutsi began leaving the country to escape the Hutu purges, settling in the four neighbouring countries Burundi, Uganda, Tanzania and Zaire. These exiles, unlike the Banyarwanda who migrated during the pre-colonial and colonial era, were regarded as refugees in their host countries, and began almost immediately to agitate for a return to Rwanda. They formed armed groups, known as "inyenzi" (cockroaches), who launched attacks into Rwanda; these were largely unsuccessful, and led to further reprisal killings of Tutsi and further Tutsi exiles. By 1964, more than 300,000 Tutsi had fled, and were forced to remain in exile for the next three decades. Pro-Hutu discrimination continued in Rwanda itself, although the violence against the Tutsi did reduce somewhat following a coup in 1973. The Twa, the minority class of the Banyarwanda, remained marginalised, and by 1990 were almost entirely forced out of the forests by the government; many became beggars.