Crimea braced for a referendum Sunday on whether to leave Ukraine and join Russia, escalating a Cold War-style security crisis on Europe's eastern edge that has left diplomacy in disarray.
Around 1.5 million people are being called to vote on the rugged diamond-shaped peninsula, which is inhabited mostly by ethnic Russians.
The choice is between becoming part of Russia or taking more powers but staying in Ukraine — and a vote for the status quo is not an option.
Polls open at 8 a.m. and close at 8 p.m., with initial results soon after — although rehearsals for the big day including the slogan "We are in Russia!" beamed onto a government building left no doubt as to the outcome.
The West has said it will not recognize the referendum, while Moscow insists it is an example of self-determination like Kosovo.
Russian troops and pro-Moscow militias took control of the strategic peninsula soon after the Kremlin-backed Ukrainian president Viktor Yanukovych fled Kiev last month after three months of deadly protests against his rule.
Ukrainian military bases in the region — home to Russia's Black Sea Fleet since the 18th century — are surrounded but there has been no armed confrontation and it is not clear what will happen to them after the vote.
There have been several attacks on journalists and pro-unity activists condemned by Amnesty International as "extremely worrying".
Washington has dismissed a vote "under the barrel of a gun" and the new government in Ukraine has branded it "illegitimate" and is concerned Moscow is trying to stir up a wider rebellion in Russified parts of eastern Ukraine.
Three activists have been killed in the eastern cities of Donetsk and Kharkiv in the run-up to the Crimea referendum and supporters of Russia have called for similar separatist polls to be held in other Ukrainian regions.
Russian lawmakers have given the go-ahead for President Vladimir Putin to invade Ukraine when he wants, citing the need to defend ethnic Russians against ultra-nationalist radicals.
Ukraine is on full combat alert and on the eve of the vote it accused Russian forces of seizing a village just outside Crimea saying: "Ukraine reserves the right to use all necessary measures to stop the military invasion by Russia".
The diplomatic wrangling and brinksmanship over Crimea have been startling, including a confrontation at the United Nations Security Council in which Ukrainian Prime Minister Arseniy Yatsenyuk asked: "Do the Russians want war?"
Successive rounds of negotiations between US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov have failed and Kerry appeared to break diplomatic protocol by not showing up for planned talks in Moscow.
While the West has been powerless to stop annexation, Russia faces a painful round of sanctions against top officials that Washington and EU nations are set to unveil on Monday and it could be ostracized or even ejected from the Group of Eight leading world powers.
Local authorities are calling this a "Crimean Spring" but many Crimeans are simply confused and concerned about the future of their Black Sea region, which will not be recognised by much of the international community.
Crimea would not automatically join Russia after the vote although officials said they would make a formal application this week.
Local leader Sergiy Aksyonov on Friday said the procedure could take "a year maximum" and has tried to reassure people that there will not be financial and legal chaos after the vote.
Ukraine's government has said Crimea cannot survive on its own -- especially since it depends on electricity, energy and water supplies from the mainland.
But Aksyonov and others have said they can easily cope -- with Russian help.
"Whether we stay with Ukraine or go with Russia, it's understandable that people are concerned," said Aleksiy Yefremov, head of the student association "New People of Crimea".
"We do not have enough information. Do we listen to official Kiev or to the local authorities?"