Ukraine crisis: Russia pledges to 'retaliate against sanctions' as Ukrainian president says Crimea vote will not be recognised

Counter-threat comes as number of Russian troops in Crimea now stands at 30,000 as US warship heads to the Black Sea

Several hundred chanting demonstrators, many waving blue-and-yellow Ukrainian flags, gathered outside the White House on Thursday to protest Russia's intervention in Crimea (EPA)

Russia has pledged to retaliate against any sanctions imposed on it by the EU and US, further raising tensions in what has quickly become worst diplomatic crisis between Russia and the west since the end of the Cold War.

Russia on Friday accused the European Union of taking an “extremely unconstructive position” by freezing talks on easing visa barriers and suspending trade in response to the country's intervention in Ukraine.

“Russia will not accept the language of sanctions and threats” and will retaliate if sanctions are imposed, the Russian Foreign Ministry said in a statement.

The comments came before reports that armed men had entered and taken control of a Ukrainian military post in Crimea on Friday, but shots had not been fired.

Russia now has 30,000 troops in Ukraine's Crimea region, Ukrainian border guards said on Friday, nearly twice the previous figure given by the government in Kiev.

In a coordinated effort, US President Barack Obama on Thursday night ordered sanctions on Russian and Ukrainian peoples involved in Moscow's military intervention in Crimea, including travel bans and freezing of their US assets.

Both the US and EU said sanctions will be furthered if Russia does not withdraw its forces back to their base in Crimea.

In an hour long phone call with Barack Obama shortly after the US President announced the punitive measures, Mr Putin brushed western threats aside, defending Russia’s intervention in Ukraine as consistent with international law.

A statement published on the Kremlin website early on Friday said that during the call, Mr Putin condemned the newly formed Kiev government as the result of an “anti-constitutional coup” and said Russia was “ unable to ignore” requests for protection from Ukraine's Russia-leaning east and south.

During the phone call, Mr Obama said the situation could be solved diplomatically in a way that addressed the interests of Russia, Ukraine and the international community, according to the White House.

A US warship is now en route to the Black Sea, in what the US military has described as a "routine" deployment scheduled well before the crisis in Ukraine.

Crimea is home to Russia's important Black Sea military base in Sevastopol. The US announced the deployment after the Pentagon unveiled plans to put more US fighter jets on a NATO air patrol mission in the Baltics in an apparent bid to reassure eastern European allies.

Separately, Ukraine's interim prime minister Arseniy Yatsenyuk on Friday told the Crimean parliament that “no-one in the civilised world” will recognise its region wide referendum on joining the Russian Federation.

In a meeting with the head of the Crimean parliament earlier on Friday however, the speaker of Russia's upper house of parliament said Crimea would be welcomed as an equal part of Russia if the region votes to leave Ukraine.

Earlier this week MPs in the autonomous Crimea region abruptly voted to join the Russian Federation and announced a March 16 region wide referendum in order to strengthen their position.

The US and EU have claimed such referendum would be against the Ukrainian constitution and in violation of international law.

Mr Putin said earlier this week that Russia had no intention of annexing Crimea, but insisted its population has the right to determine the region's status in the referendum.

Wading into the debate, China, which often stands with Russia on many global issues, said on Friday that sanctions are not the best way to resolve the crisis.

US officials said a list of people targeted by the sanctions had not yet been drawn up but added that the Russian President would not be one of them.

The order targets any assets held in the US by “individuals and entities” responsible for the Russian military intervention in Ukraine, threatening its territorial integrity or seeking to assert governmental authority over any part of Ukraine, without authorisation from the government in Kiev.

Mr Obama, appearing in the White House press room hours after signing the order, said the US sanctions were meant to impose costs on Russia for its actions.

Russia's Foreign Ministry meanwhile has branded NATO's decision to curb its corporation with Russia as a “biased and prejudiced approach”.

“We see as extremely dangerous attempts to bring in the 'NATO factor' to Ukraine, where the situation is complex and delicate as it is, as it creates additional tension and undermines the prospects for settling the situation,” the ministry said in a statement.