German Chancellor Angela Merkel called on Russia on Wednesday not to do anything to destabilize the situation in Ukraine after pro-Moscow forces took de-facto control of Ukraine's majority Russian Crimean Peninsula.

"Russia must desist from any taunting which could lead to a destabilization of the situation," Merkel's spokesman Steffen Seibert told a government news briefing.

Germany's military will fly around 50 Ukrainians injured during unrest in central Kiev to the EU country for treatment, officials said Wednesday.

The move follows a request by the Ukrainian government to the German embassy in Kiev for help with the group, the defense ministry said in a statement.

The Organization for Security and Co-operation in Europe (OSCE) said Wednesday it was sending a mission of 35 military observers to Ukraine.

"It is my hope that this military visit will help to de-escalate tensions in Ukraine," OSCE Secretary General Lamberto Zannier said in a statement.

Ukraine is reinforcing security measures at its nuclear power plants in response to Russian threats, Ukraine's ambassador told the U.N. atomic agency in a letter seen by Agence France Presse on Wednesday.

"Illegal actions of the Russian armed forces on the Ukrainian territory and the threat of force amount to a grave threat to security of Ukraine with its potential consequences for its nuclear power infrastructure," Ihor Prokopchuk said.

Russia sold a record $11.3 billion in foreign currency to support the ruble on March 3, when the ruble came under unprecedented pressure due to concerns about conflict in Ukraine, central bank data showed Wednesday.

The Russian central bank sold foreign currency to buy rubles and prevent the Russian currency from falling further in value, after the market reacted with panic to parliamentary approval for President Vladimir Putin's request to allow military action in Ukraine on what has been dubbed "Black Monday".

Australia has offered temporary refuge to visiting Ukrainians due to soon return to their country, which is in turmoil.

Foreign Minister Julie Bishop told Parliament on Wednesday that Ukrainian nationals could apply for visa extensions to stay temporarily in Australia "while their nation is under threat."

Canada's Prime Minister Stephen Harper on Tuesday ordered the suspension of joint military exercises with Russia, over Moscow's troop intervention in Ukraine's Crimea region.

"I have this morning directed that, effective immediately, all planned bilateral activities between the Canadian Armed Forces and the military of the Russian Federation be suspended," Harper said in a statement.

EU foreign policy chief Catherine Ashton held "useful" talks in Madrid Tuesday with Russian Foreign Minister Sergei Lavrov over the spiraling crisis in Ukraine, a European source said.

"We had a useful discussion which lasted over an hour," a European diplomatic source quoted Ashton as saying after the meeting held in the Russian ambassador's residence in Madrid.

Russian President Vladimir Putin has calmed fears of an imminent war between Russia and Ukraine's new authorities but also made clear that Moscow has no intention of loosening its new grip on Crimea in defiance of Western anger.

Breaking an uncharacteristic silence since the downfall of president Viktor Yanukovych 10 days ago, Putin on Tuesday displayed no fear of a prolonged crisis in ties with the West over the situation in the Ukrainian region of Crimea which is now controlled by pro-Moscow forces.

Ukraine's 150,000 ethnic Hungarians, feared as potential fifth columnists for ousted president Viktor Yanukovych, face a growing threat from far-right nationalists.

In the region of western Transcarpathia, the large Hungarian minority has grown increasingly uneasy.