Tensions are mounting ahead of a planned referendum Sunday to determine whether or not Crimea will break from Ukraine and join Russia.

A few updates on the situation…

From AFP via Yahoo News:

Ukraine accused Russia on Saturday of invading a region bordering Crimea and vowed to use “all necessary measures” to ward off an attack that came on the eve of the peninsula’s breakaway vote.

The dramatic escalation of the most serious East-West crisis since the Cold War set a tense stage for the referendum on Crimea’s secession from Ukraine in favour of Kremlin rule — a vote denounced by both the international community and Kiev.

The predominantly Russian-speaking Black Sea region of two million people was overrun by Kremlin-backed troops days after the February 22 fall in Kiev of a Moscow-backed regime and the rise of nationalist leaders who favour closer ties with the West.

President Vladimir Putin defended Moscow’s decision to flex its military muscle by arguing that ethnic Russians in Ukraine needed “protection” from violent ultranationalists who had been given free reign by the new Kiev administration.

But Russian Foreign Minister Sergei Lavrov had told Secretary of State John Kerry in London on Friday that Moscow “has no, and cannot have, any plans to invade the southeast region of Ukraine.”

The full statement from the Ministry of Foreign Affairs of Ukraine website demanded Russia withdraw forces from the territory of Ukraine immediately.

“Ministry of Foreign Affairs of Ukraine expresses its strong and categorical protest against the landing on March 15, 2014 near the village Strilkove, Kherson region of troops of the Russian Federation Armed Forces in a number of 80 military personnel, and seizure of the village Strilkove with the support of 4 helicopter gunships and 3 armored combat machines,” the statement read.

“Ukraine Foreign Ministry declares the military invasion by Russia and demands the Russian side to immediately withdraw its military forces from the territory of Ukraine.”

“Ukraine reserves the right to use all necessary measures to stop the military invasion by Russia.”

Also on Saturday, the United Nations Security Council voted on a draft resolution declaring Sunday’s planned referendum on Crimea’s status invalid.  Russia vetoed the resolution, while China abstained.

From the Associated Press via ABC News:

Russia vetoed a U.N. resolution declaring Sunday’s referendum on the future of Ukraine’s Crimean Peninsula illegal, and close ally China abstained, underlining Moscow’s international isolation.

Supporters of the U.S.-sponsored resolution knew Russia would use its veto. But they put the resolution to a vote Saturday morning to show the strength of opposition to Moscow’s takeover of Crimea in the U.N. Security Council and got China to abstain rather than join Russia in casting a veto, which it did on three Western-backed resolutions on Syria.

The final vote on Saturday was 13 members in favor, China’s abstention, and Russia as a permanent council member using its veto.

“The resounding message from today’s vote is that Russia stands isolated in this council and in the international community,” Britain’s U.N. Ambassador Mark Lyall Grant told the council after the vote.

“Russia alone backs this referendum. Russia alone is prepared to violate international law, disregard the U.N. Charter and tear up its bilateral treaties,” he said. “This message will be heard well beyond the walls of this chamber.”

The New York Times explained Friday that there are Two Choices in Crimea Referendum, but Neither Is ‘No’.

Meanwhile, CNN reports that there were rival rallies in Ukraine’s eastern city of Donetsk and in Russia in Moscow on Saturday.

[Featured image: AP/UNTV video from WSJ, via Yahoo]