During the Soviet era, an autonomous oblast within the Azerbaijan SSR governed the predominantly Armenian-populated region. As the Soviet Union began to disintegrate during the late 1980s the question of Nagorno-Karabakh's status re-emerged, and on 20 February 1988 the parliament of the Nagorno-Karabakh Autonomous Oblast passed a resolution requesting transfer of the oblast from the Azerbaijan SSR to the Armenian SSR. Azerbaijan rejected the request several times, and ethnic violence began shortly after with a series of pogroms between 1988 and 1990 against Armenians in Sumgait, Ganja and Baku, and against Azerbaijanis in Gugark and Stepanakert. Following the revocation of Nagorno-Karabakh's autonomous status, an independence referendum was held in the region on 10 December 1991. The Azerbaijani population, which then constituted around 22.8% of the region's population boycotted the referendum. 99.8% of participants voted in favour. In early 1992, following the Soviet Union's collapse, the region descended into outright war.