PEREVALNOYE, Ukraine (CNN) — Residents of Ukraine's Crimea region headed to the polls Sunday to vote in a disputed referendum on whether to join Russia or become an effectively independent state connected to Ukraine.
Beyond the question of Crimea's future status, the vote will likely influence future international relations in the region and beyond -- having put the United States and Russia on the kind of collision course not seen since the end of the Cold War.
Preliminary results could come as soon as Sunday night local time. The United States, which says the vote is illegal, has already said it expects the Black Sea peninsula's majority ethnic Russian population to vote in favor of joining Russia. Moscow has strongly backed the referendum.
Kicking off the polling in a prerecorded statement, Crimean Prime Minister Sergey Aksyonov called on the residents of Crimea to cast their vote "independent of nationalism and disintegration."
Aksyonov acknowledged that the "eyes of the entire world are on us today." He asked Crimeans to show their aspiration to "live free in the world with friendly relations with all."
At a polling station in Perevalnoye, near a military base, a steady stream of voters arrived to cast their ballots despite the wintry weather.
Blaring dance tunes and Russian folk music welcomed them to the polling station, in an echo of Soviet times. What appeared to be a group of Russian soldiers -- without identifying insignia but with Russian license plates on their vehicles -- stood nearby.
Svetlana Kalisetskaya, head of the electoral commission there, told CNN that "compared to other elections, it is much livelier and friendlier."
One voter, Grigory Illarionovich, told CNN, "I'm for restoring Crimea to Russia. Returning what Khrushchev took away."
The Black Sea peninsula was part of Russia until Soviet leader Nikita Khrushchev gave it to Ukraine in 1954. Ukraine was then part of the Soviet Union.
'Russia is an opportunity'
Another voter in Perevalnoye, Viktor Savchenko, said he would never vote for the government in Kiev. "I want us to join Russia, and live like Russians, with all their rights," he said.
Victoria Khudyakova said she also had voted to join Russia, which she sees as being "spiritually close" to Crimea. "For me, Russia is an opportunity for our Crimea to develop, to bloom. And I believe that it will be so," she said.
As of 3 p.m. (9 a.m. ET), voter turnout for all of Crimea stood at 63.9% of eligible voters, with 970,019 votes cast so far, Mikhail Malyshev, the head of the Crimean Election Commission, told reporters in the regional capital, Simferopol.
But Ukraine's Prime Minister Arseniy Yatsenyuk, speaking in Kiev, dismissed the referendum as illegitimate under Ukrainian and international law, and improperly run.
He said Ukrainian authorities had information from Crimea about voting irregularities, including people who are not Crimean citizens casting ballots, absence of proper monitoring and the presence of armed men.
Malyshev said there was no information that people with foreign passports were voting in the referendum. He also said no "provocations" had been reported at polling stations.
In Simferopol, voters filed into a polling place, picked up white and yellow ballots and headed to private booths to fill them out before dropping them through the slits of clear ballot boxes.
In another polling station, the vast majority of ballots dropped in the boxes appeared to be marked in favor of joining Russia.
Some 80% of voters turning out at a polling station in Bakhchysaray were not on the electoral roll, the registrar told CNN. Those not on the roll have their passport and papers checked to establish identity. On the spot, election staff decide, with a show of hands, whether to allow those voters to participate.
A CNN team photographed one voter dropping two pieces of paper into the ballot box, raising questions over how effectively the vote is being monitored.
Turnout is high, but many Crimean Tatars, an ethnic Turkic group with deep roots on the peninsula, are boycotting the vote, as are many ethnic Ukrainians.
Tatars, who make up about 12% of the Crimean population, have faced severe persecution in the past, when Crimea belonged to Russia. On Saturday, representatives issued a statement recognizing Ukraine with its present borders, which would include Crimea.
They asked the Ukrainian parliament in Kiev for more legal protection for their ethnic group.
Much pro-Russian propaganda has been in evidence in the run-up to the referendum, both on the airwaves and in the form of campaign posters showing the Crimean Peninsula painted with either a Nazi swastika or the Russian flag.
Moscow has insisted it has the right to protect ethnic Russians in Ukraine, who it claims are threatened by radical nationalists and "fascists."
Pro-Russian troops remain firmly in control of the Black Sea peninsula. Ukraine and the West insist the soldiers belong to Moscow, but the Kremlin vehemently denies it, saying they are Crimean "self-defense" forces.
Russia tightened its military grip Saturday. About 60 Russian troops in six helicopters and three armored vehicles reportedly crossed into Ukraine's Kherson region and were in the town of Strilkove, on a strip of land just northeast of Crimea.
The region is key to neighboring Crimea, because it gets electricity, fresh water and natural gas from there. The Russians said they were in Kherson to prevent a possible terrorist attack on oil assets in the area, according to the Ukrainian border guards.
German Chancellor Angela Merkel criticized Russian activities in Kherson in a phone call with President Vladimir Putin on Sunday, according to a statement from her office.
She urged an increase in the presence on the ground of military observers from the Organization for Security and Co-operation in Europe, so they can quickly be sent to contested areas, especially in eastern Ukraine.
In light of the failure to achieve a "contact" group to aid talks, Merkel reiterated the need for direct negotiations between the governments of Russia and Ukraine to resolve the situation, the statement said.
Ukraine's acting Defense Minister Ihor Tenyukh told a Cabinet meeting Sunday that there are now 21,500 Russian troops on Crimean soil. Russia is entitled to station 25,000 troops at its leased Sevastopol naval base -- but the question is where those troops are.
Tenyukh also said Ukrainian troops and equipment are being moved into Ukraine's east and south, in line with where Russian military forces are located.
Moscow has been carrying out mass military exercises not far from Ukraine's eastern border.
Saturday, Russia wielded its veto power as a permanent member of the U.N. Security Council against a U.S. draft resolution that declared Sunday's Crimea referendum invalid.
Thirteen of the 15 Security Council members backed the resolution, while China abstained.
"The reason only one country voted 'no' today is that the world believes that international borders are more than mere suggestions," said U.S. Ambassador Samantha Power after the vote.
Russian Ambassador Vitaly Churkin argued that Crimean citizens had a right to self-determination.
What happens next in Crimea?
If the vote goes in favor of joining Russia, Crimea's government will declare its independence and ask Moscow to let it join the Russian Federation. Russian lawmakers have said they'll vote on the question on Friday.
In Simferopol and other places with Russian majorities, blue, white and red Russian flags have dominated the streets.
In the coastal Crimean town of Sevastopol, where Russia maintains its Black Sea fleet, concerts on the main square have been celebrating the return to the "motherland" this past week.
"Everybody believes the results are already rigged," said CNN iReporter Maia Mikhaluk from Kiev.
"People are concerned what is going to happen after the referendum," she said. "People are concerned that the Russian army will use force, guns to push (the) Ukrainian army from Crimea."
Ukraine's acting foreign minister, Andrii Deshchytsia, repeated Saturday that Kiev's position that it is engaged in a "diplomatic war" with Russia, but is looking for a peaceful resolution to the crisis in Crimea.
In the city of Donetsk, near the Russian border in eastern Ukraine, pro-Russian demonstrators stormed the prosecutor's office, forcing their way through a door of the building.
The activists are demanding the release of pro-Moscow movement leader Pavel Gubarev, who was arrested on March 6 for leading an occupation of the regional administration office.
Earlier, thousands of pro-Russian demonstrators gathered for a second day in a central Donetsk square before marching through the city. Riot police stood on guard outside the offices of Ukraine's security service and the regional administration.
Addressing the Cabinet meeting, acting Interior Minister Arsen Avakov said the rallies in Donetsk and another nearby city, Lugansk, were small and had already ended.
About 4,000 pro-Russian protesters have gathered for a third rally, in Kharkiv, he said.
Lavrov: Referendum is legal
Russia has come under concerted international pressure to halt its activities in Crimea -- despite its denials that it is directly involved -- and talk to the interim government in Kiev.
But, so far, it has refused to budge. Talks between U.S. Secretary John Kerry and Russian Foreign Minister Sergey Lavrov ended in disagreement.
After a call with Kerry on Saturday, Lavrov said in a statement that Crimea's referendum conforms to international law.
European nations and the United States have announced some targeted punishments against Russia and have threatened tougher sanctions if the secession vote goes through.
In addition, the West is shoring up Ukraine with offers of billions in aid to its fledgling government.
Kiev's new Western-leaning government, which came to power following the ouster of President Viktor Yanukovych, has insisted that Ukraine's territorial integrity, including Crimea, must be respected.