The Donetsk People's Republic, which arose in chaotic and murky circumstances in early April, claims to want full autonomy from Ukraine, which they say has been led by a "fascist junta" since Donetsk region native Yanukovych was toppled.
To that end, insurgent election officials say some 3 million ballot papers have been printed for the vote that asks one question: "Do you support the act of proclamation of independent sovereignty for the Donetsk People's Republic?"
Despite the phrasing, organizers say they decide only after the vote whether they want independence, greater autonomy within Ukraine or annexation by Russia.
Russian state media describe the Donetsk People's Republic movement as "supporters of federalization," reflecting Moscow's official line that it would like Ukraine's government to devolve some powers to the regions. But many in Donetsk say they would like their would-be republic to one day join their eastern neighbor. The Russian tricolor often flutters over the several dozen government offices seized and occupied by anti-government groups.
If Putin chooses to dash the hopes of those in his own country and in eastern Ukraine who crave another Crimea-style annexation, his now sky-high approval ratings could suffer. But pursuing expansionist goals, or even tacitly supporting anti-government movements in Ukraine, will likely prompt new and substantially more punitive Western sanctions against Russia.
Donetsk People's Republic elections chief Roman Lyagin said there will be around 1,200 polling stations and he expects a turnout of 70 percent.
"Preparations are going according to schedule. Almost the entire run of ballots has been prepared," said Lyagin told The Associated Press.
Campaigning for the referendum has been negligible, largely relying on crude graffiti. Many sidewalks bear spray-painted stencil images of the word "referendum" next to a crossed-out swastika.
The Donetsk People's Republic has its own radio and television stations and a fledgling online presence, all of which have churned out a steady diet of anti-Kiev invective.
The Donetsk People's Republic was formed April 7 by pro-Russia activists after the storming of a regional administrative building. In subsequent days, heavily armed men began storming police stations and city halls. Journalists, activists and politicians sympathetic to the government started to go missing. Horlivka city council representative Volodymyr Rybak turned up dead, bearing signs of torture.
A climate of fear has grown, fueled by the now-common sight of gunmen roaming even the regional capital, Donetsk.
"We are remaining quiet, because we are simply afraid for our lives," said Diana Dekatiryova, a university student. "The thought I have is to stay away from the referendum, because nothing will depend on our vote anyway."
The resolve of many pro-Russians has been emboldened by Ukrainian government operations to militarily recapture Slovyansk, a city 110 kilometers (70 miles) north of Donetsk and under the control of the armed Donetsk People's Republic.
A view shared by many anti-government activists — and eagerly promoted by Kremlin-backed television — is that Ukrainian authorities are shooting people who just want closer relations with Russia.
"They can't kill everybody. We must cry out. The whole world must learn about this," said Tamara Soynikova, 59, member of a Donetsk People's Republic election panel in the city of Kostiantynivka.
In contrast, pro-Ukrainian sentiments are especially pronounced among the younger generation, those with no memory of living in the Soviet Union.
"We were born in Ukraine, we live in Ukraine. What does it matter that we're Russian?" said first-year law student Arkady Sabronov, 18.
Vladimir Isachenkov in Moscow contributed to this report.
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