On 25 September 1961, a referendum was held to establish whether Rwanda should become a republic or remain a kingdom. Citizens voted overwhelmingly for a republic. After parliamentary elections held on the same day, the first Rwandese Republic was declared, with Kayibanda as prime minister. Mbonyumutwa was named the first president of the transitional government.

Between 1961 and 1962, Tutsi guerrilla groups staged attacks into Rwanda from neighboring countries. Rwandan Hutu-based troops responded, and thousands more were killed in the clashes. On 1 July 1962, Belgium, with UN oversight, granted full independence to the two countries. Rwanda was created as a republic governed by the majority MDR-Parmehutu, which had gained full control of national politics. In 1963, a Tutsi guerrilla invasion into Rwanda from Burundi unleashed another anti-Tutsi backlash by the Hutu government; their forces killed an estimated 14,000 people [1]. The economic union between Rwanda and Burundi was dissolved and tensions between the two countries worsened. Rwanda became a Hutu-dominated one-party state.

Source: Wikipedia, published under the GNU FDL. Retrieved 2014-03-03


Notes:
[1] See Burundi Civil War