The disputed region of Nagorno-Karabakh, with its ethnic Armenian majority, is a de jure part of Azerbaijan, but is de facto held by the self-proclaimed Republic of Artsakh, which is supported by Armenia. Ethnic violence began in the late 1980s, and exploded into a war following the dissolution of the USSR in 1991. On 20 February 1988, the Soviet of the Nagorno-Karabakh Autonomous Oblast passed a resolution requesting transfer of the oblast from the Azerbaijan SSR to the Armenia SSR; Azerbaijan rejected the request. Following the revoking of Nagorno-Karabakh's autonomous status, an independence referendum was held on 10 December 1991 which was boycotted by the Azerbaijani population which then constituted around 22.8% of Nagorno-Karabakh's population; as a result, 99.8% voted in favor. Both Armenia and Azerbaijan then became fully independent of the Soviet Union in 1992.