The referendum is being brought forward from March 30, the region's deputy prime minister, Rustam Temirgaliyev, told reporters in Simferopol, according to Russian news agencies.
He said voters will have two options: Either to vote for Crimea becoming part of the Russian Federation, or to vote for the return of the region's 1992 constitution, which laid down Crimea as an autonomous region within Ukraine.
DPA