The hold of Kiev's new Western-backed leaders on the separatist region loosened still further when pro-Kremlin gunmen seized the air traffic control tower at Crimea's main international airport and cancelled all flights except for those to and from Moscow.
The latest escalation of Europe's worst crisis in decades came moments after ousted president Viktor Yanukovych defiantly vowed to return to Kiev from Russia and declared he was still the head of the ex-Soviet state.
The strategic region's self-declared rulers are recruiting volunteers to fight Ukrainian soldiers while the Russian parliament today prepared legislation that would simplify the Kremlin's annexation of Crimea after next Sunday's vote.
But Kiev rejects the referendum and is appealing to Western powers for both diplomatic backing and pressure on Moscow to release its troops' stranglehold on Crimea.
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The European Union also announced trade breaks for Ukraine equivalent to USD 690 million that could ease its burden from trade restrictions that Russia has threatened in response to Kiev's told toward the West.
The deep historic divide in the nation of 46 million between its pro-European west and more Russified southeast became ever more apparent as Ukraine's political crisis unfolded following Yanukovych's rejection in November of an historic EU pact in favour of better relations with the Kremlin.
Last month's rise to power in Kiev of nationalist leaders with cultural and political links to Europe prompted Putin to seek the right to use force against Ukraine in defence of the country's Russian speakers.