Russian news outlets and state media reported that 93 percent of voters had supported joining the Russian Federation. According to regional election authorities, the number was 95.5 percent with about half of ballots counted. Turnout was put at 83 percent, a high figure considering that many opponents of the motion had pledged to boycott the ballot. The full official results were not expected until Monday morning.

Japan became the latest country to reject the referendum's validity early on Monday morning. Top goverment spokesman Yoshihide Suga said Japan would "strongly urge" Russia not to annex Crimea and would cooperate with other Group of Seven members in dealing with the issue. Russia currently holds the rotating G8 presidency, but other members have suspended preparations for a planned summit in Sochi this June as a result of the situation in Crimea.

The White House issued a statement late on Sunday saying that President Barack Obama had told his Russian counterpart Vladimir Putin that Washington did not recognize the referendum's results.

"He [Obama] emphasized that Russia's actions were in violation of Ukraine's sovereignty and territorial integrity and that, in coordination with our European partners, we are prepared to impose additional costs on Russia for its actions," the White House statement said.

Canadian Prime Minister Stephen Harper issued a statement saying that the "so-called referendum ... was conducted with Crimea under illegal military occupation."

The European Commission in Brussels similarly said it would take steps against Russia over the controversial poll.

"The referendum is illegal and illegitimate and its outcome will not be recognized," European Council President Herman Van Rompuy and Commission President Jose Manuel Barroso said in a joint statement.

EU foreign ministers prepare response

EU foreign ministers are scheduled to meet on Monday to decide whether to impose sanctions such as visa bans and asset freezes on Russian authorities.

Speaking on ZDF public television on Sunday evening, German Foreign Minister Frank-Walter Steinmeier said Russia's "preparations for an annexation of Crimea" were "completely unacceptable." Steinmeier said that his European colleagues in Brussels now faced decisions that would not be easy on Monday.

"We have signalled to Russia that we are not interested in a confrontation by asking [Moscow] to calm down and seek a way that we - the international community, Ukraine and Russia - can step back from this escalation," Steinmeier said. "Russia has not made use of any of these options, and therefore there will be a meeting tomorrow in which decisions must surely be taken."

When pressed on these consequences, Steinmeier said that a next step "would indeed include measures in the region of sanctions" from the EU, suggesting a "gradual approach" to this process. He also warned against "short-term hopes" of quickly changing the situation in Crimea, saying "I assume Russia has made all the preparations to bring Crimea into Russian territory."

Putin defends referendum

Russian President Vladimir Putin insisted that the referendum was legal and told German Chancellor Angela Merkel by telephone on Sunday that it was being "implemented in full compliance with international law."

Merkel told Putin that the presence of the Organization for Security and Co-operation in Europe (OSCE) should be "swiftly expanded" on Crimea.

Ukrainian Prime Minister Arseniy Yatsenyuk repeated Merkel's call for more OSCE observers. "Their mandate should include the east and south of Ukraine, including Crimea," Yatsenyuk said in a statement.

Earlier on Sunday, the news agency AFP reported on possible irregularities in the referendum, alleging that voters had been 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.

Crimea's Moscow-backed prime minister denied claims that the vote was not fair or transparent. Sergei 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."

Ukraine's acting defense minister, Ihor Tenyukh, told reporters in Kyiv that the Ukraine and Russian defense ministries had 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," Tenyukh said.

msh, jr/lw (AFP, Reuters, AP, dpa)