All updates in Universal Coordinated Time (UTC)

19:21 - That's all for DW's live blogging of Sunday's vote in Crimea. You can head here for developing and breaking news on the referendum and further international reaction.

18:37 - White House press secretary Jay Carney says the US rejects "the 'referendum' that took place in the Crimean region of Ukraine."

18:30 - Aksyonov tweets that voters have made "history."

18:19 - Mikhail Malyshev, the Chairman of the Electoral Commission, is speaking to journalists. Giving an update on figures and the timeframe in which results will be released. Russian news outlets and state media are reporting that 93 percent of voters supported the union with Russia.

18:00 - Polls in Crimea have now closed.

17:55 - Five minutes until polls close in Crimea.

17:10 - Sergej Aksyonov, Crimea's Moscow-backed prime minister, tweets that "turnout two hours before the polls close was 73.4 percent."

17:00 - One hour to go until polling stations close in Crimea.

16:35 - News agencies are quoting an unnamed US State Department official, on a phone conversation between the top diplomats of the US and Russia. The official says Secretary of State John Kerry told Russian Foreign Minister Sergei Lavrov the US would not accept the results of Crimea's referendum, and urged Moscow to pull back Russian forces in Crimea.

16:26 - Electoral authorities have put voter turnout in Crimea at around 64 per cent, news agency AFP says.

16:19 - Van Rompuy and Barroso say EU foreign ministers will gather on Monday to decide on possible measures against Russia. Have called on Moscow to withdraw armed forces from Crimea.

16:18 - EU President Herman Van Rompuy and European Commission President Jose Manuel Barroso say in a joint statement that "the solution to the crisis in Crimea must be based on territorial integrity, sovereignty and independence of Ukraine."

16:15 - The EU executive in Brussels says the bloc will not recognize the outcome of the referendum in Crimea.

15:57 - There's still two hours to go until polls close in Crimea, but that hasn't stopped celebrations beginning in Simferopol, tweets DW correspondent Mareike Aden.

15:51 - As reported earlier, German Chancellor Angela Merkel told Russian President Vladimir Putin by phone on Sunday that more international observers are needed in Ukraine.

15:18 - As the Sochi Winter Paralympics draw to a close today, the president of Ukraine's national Paralympic Committee, Valeriy Sushkevych, has spoken to DW about his fears once the Games are over.

14:27 - German government spokesman Steffen Seibert says Putin had a "positive assessement of this initiative," namely to expand the OSCE's presence in Ukraine.

14:26 - Ukrainian Prime Minister Arseniy Yatsenyuk has repeated German Chancellor Angela Merkel's call for more OSCE observers. "Their mandate should include the east and south of Ukraine, including Crimea," Yatsenyuk said in a statement - AFP.

14:05 - The pro-Russian demonstrations in Ukraine's eastern city of Donetsk appear to be moving fast. @mike_giglio tweets that it appears the demonstrators have taken control of the prosecutor's building and are moving on to the regional government building "they've occupied twice in the past."

13:52 - Now the German government has released a statement about Angela Merkel and Vladimir Putin's telephone conversation earlier on Sunday. Merkel told Putin that the existing OSCE presence in Ukraine should be expanded swiftly, especially in the east, Reuters says.

13:47 - DW's news team will be updating this live blog throughout the Crimean vote on Sunday afternoon, and into the evening. If you'd like to read some background information on the referendum, head over here.

13:38 - Yatsenyuk's cabinet meeting speech in more detail: "I want to say above all ... to the Ukrainian people: Let there be no doubt, the Ukrainian state will find all those ringleaders of separatism and division who now, under the cover of Russian troops, are trying to destroy Ukrainian independence." - Reuters

13:32 - Strong words from Ukrainian Prime Minister Arseniy Yatsenyuk, who Reuters says has promised on behalf of the government to track down and bring to justice all those promoting separatism in Crimea.

13:27 - The Kremlin statement says Putin expressed concern over tensions in Ukraine's south and southeast, which he says were caused by "radical groups."

13:23 - Russian President Vladimir Putin has told German Chancellor Angela Merkel by phone that the referendum in Crimea complies with international law, and that Russia will respect the choice of Crimeans in the vote - Kremlin statement.

13:16 - Acting Ukrainian interior minister Arsen Avakov has said that Ukraine's border with Russia is now nearly complely closed, tweets Kyiv Post reporter @isaacdwebb.

13:09 - AFP is reporting on possible irregularities in the Crimea referendum, saying voters were seen casting their ballots before the official opening of polls, and that there had been 'blatant' campaigning for Russia - something not allowed under election rules.

12:55 - The Crimean prime minister has denied claims the vote is not fair or transparent. Sergej Aksyonov spoke as he cast his ballot this morning: "There is no pressure on people, you can see that for youself. People are free to vote. Personally, I haven't seen or felt any pressure."

12:52 - this in from Reuters: Ukraine's acting defense minister Ihor Tenyukh has told reporters in Kyiv that the Ukraine and Russian defense ministries have agreed on a truce in Crimea until Friday, March 21. "No measures will be taken against our military facilities in Crimea during that time. Our military sites are therefore proceeding with a replenishment of reserves."

12:37 - DW correspondent Mareike Aden has given a glimpse inside a ballot box in Crimea. "Majority of those who attend vote "yes" for Russia," Mareike tweets.

12:30 - @lindseyhilsum, Britain's Channel 4 international editor, has tweeted a picture of a ballot paper that is a 'no' to joining Russia. Says it's the first he's seen.

12:21 - Pro-Russia demonstrations happening in the eastern Ukrainian city of Donetsk. That's where one person was killed on Thursday when pro-Kyiv demonstrators were allegedly attacked by a pro-Russia group.

12:11 - Ukraine's former prime minister, Yulia Tymoshenko, has told Germany's daily Der Tagesspiegel that Russia's "aggressive striving for power with regard to Ukraine represents not only a danger for the Ukraine state - other parts of eastern Europe are also in danger."

12:01 - AFP reports that Cossacks and self-defense militias were seen patrolling some polling stations in Simferopol, while others even saw Russian bikers drop in to observe the vote's progress.

11:45 - @dpeleschuk, Senior Correspondent for @GlobalPost: "#Ukraine flag flies over mil base in Simferopol, but for how much longer? I can hear echoes of rock music frm inside."

11:40 - A group based in Ukraine has claimed responsibility for launching denial-of-service (DDoS) attacks on NATO websites.

11:30 - The Interfax news agency reports that voter turnout in Crimea reached 50 percent by midday local time.

09:33 - Ukraine's interim defense minister claims that Russian troops in Crimea now number up to 22,000, allegedly in violation of a 12,500 limit set for 2014.

06:00 - Polls open in Crimea's referendum. Voters have two options: They can choose either to join the Russian Federation, or return to Crimea's political status under Ukraine's 1992 constitution, which would grant the Black Sea peninsula broader autonomy. On Saturday, Russia vetoed a UN Security Council resolution condemning the Crimean referendum as illegitimate. Thirteen of the 15 council members voted in favor of the US-drafted motion. China, which often sides with Russia, abstained from the vote.

All updates in Universal Coordinated Time (UTC)

slk, jr/mkg (AP, AFP, dpa, Reuters)