Kiev: Voting began on Sunday in referendums called by pro-Russian rebels in eastern Ukraine to split from the rest of the ex-Soviet republic, polls the US slammed as "illegal" as the West fears they could spark civil war.
The vote, carried out as two "referendums" in provinces where the insurgents hold more than a dozen towns, marks a serious deepening of the political crisis in Ukraine, which has pushed East-West relations to lows not seen since the end of the Cold War.
Although a "yes" vote would likely be recognised only by Russia, it would greatly undermine a presidential election Ukraine is to hold in two weeks, which the United States and the European Union see as crucial to restoring stability.
And they come as fighting continued in eastern Ukraine, with several explosions heard overnight in the flashpoint town of Slavyansk as the Kiev authorities try to flush the rebels from towns they control.
Troops have been battling the well-armed separatists, who have barricaded themselves in towns and cities in the two provinces where the votes are taking place: Donetsk and Lugansk.
The referendums are "illegal under Ukrainian law and are an attempt to create further division and disorder", US State Department spokeswoman Jen Psaki said in a statement late on Saturday.
The votes "violate international law and the territorial integrity of Ukraine," she stressed, adding that the United States would not recognise the result.
Earlier on Saturday, France and Germany jointly threatened "consequences" on Russia if the presidential election is scuppered — echoing US President Barack Obama's warning of automatic sanctions that would slice into whole sectors of Russia's weakening economy.
Interim Ukrainian president Oleksandr Turchynov warned that voting for independence would be a "step into the abyss" for these regions and lead to the "total destruction" of the economy there.
'100 per cent turnout'
Despite rebel claims that the polling will reach 90 per cent of the seven million people living in these two provinces, the areas they hold account for less than half that population.
They decided to go ahead with the vote despite a public request made Wednesday by Russian President Vladimir Putin to postpone it.
Polling stations opened in schools in rebel-held territory at 8:00 am and were to close 12 hours later, according to insurgent chiefs in the city of Donetsk.
The self-proclaimed mayor of Slavyansk, Vyacheslav Ponomaryov, said he expected 100 per cent turnout for Sunday's vote.
After the results come in, "the Republic of Donetsk will begin to function" and cultivate "friendly relations" with Russia, he added.
But another rebel leader, Roman Lyagin, said: "If the answer is yes, it does not necessarily mean that we will be joining Russia".
A poll released on Thursday by the Pew Research Centre in the United States suggested 70 per cent of Ukrainians in the east want to stay in a united country, while only 18 per cent back secession.
Kiev has already dismissed the vote as "illegitimate" and against the Ukrainian constitution.
However, like in Crimea — which Russia annexed in March after a similar referendum — it has been powerless to stop preparations.
One voter, Viktoria Petrovna, arrived early in the city of Donetsk to cast her vote, telling AFP: "This is an important day. They told us to come and vote, so it's essential to do that."
"We are living in very important times."
West threatens 'consequences'
The Ukrainian government and its Western backers accuse Putin of deploying Russian special forces in east Ukraine, as in Crimea, to see the vote through and to sabotage the May 25 presidential election.
Putin belatedly admitted sending military forces to Crimea but continues to deny militarily meddling in east Ukraine.
Psaki said that "we still see no Russian military movement away from the bo