Crimea's parliament has announced that it will hold a referendum in May to reconsider the region's status in the wake of the revolution that rocked Ukraine that topped president Viktor Yanukovich.
Crimea, the only Ukrainian region where ethnic Russians make up a majority of the population, will vote on greater self-rule on 25 May.
Lawmakers also voted to dismiss the regional government and appointed Serhiy Aksionov, the leader of the Russian Unity party, as new prime minister.
"As a result of an unconstitutional seizure of power in Ukraine with the support of radical nationalist armed gangs, Crimeans have felt that the peace and tranquillity of Crimea is in jeopardy," said the press secretary of the parliament speaker Oxana Korniikchuk.
"We are convinced that only by holding an all-Crimean referendum on improving the status of the autonomy and expanding its powers Crimeans will be able to determine the future of autonomy on their own."
In Kiev, Ukraine's electoral committee member Yuriy Donchenko described the move as "illegitimate", Espreso TV reported.
Sources close to Yanukovich said the fugitive president is to hold a news conference in Rostov-on-Don, southern Russia, on Friday, Itar-Tass news agency reported.
Earlier on Thursday armed men took over the regional government and parliament buildings in Simferopol and raised the Russian flag.
Tension has been mounting in the region since Kremlin-backed Yanukovich was ousted.
Russians have called on Moscow to protect them from the revolutionaries who they described as radicals and Nazis.
Fights broke out in Simferopol between Muslim Tatars, who have sided with ethnic Ukrainians in backing the revolution, and a rival group of pro-Russia demonstrators.