The new pro-Moscow leader of Ukraine’s autonomous Crimea region has asked Russian President Vladimir Putin for help to ensure peace.
A Kremlin source said it would “not leave unnoticed” the request from Sergiy Aksyonov.
Reports speak of a clash overnight in Crimea’s capital and an attempt to seize a Ukrainian missile base.
Ukraine’s interim Prime Minister, Arseniy Yatsenyuk, accused Russia of seeking to provoke an escalation.
There is still no official confirmation of who the armed men surrounding key areas in Crimea really are. They wear uniforms without insignia and drive unidentified vehicles.
Some say they are locals organising themselves into a self-defence unit against the Ukrainian uprising. But many carry heavy weapons and appear in control of armoured personnel carriers. They seem more organised than an impromptu militia.
And yet while Ukraine’s government warns that Russia has carried out a “military occupation and invasion” of Crimea, it does not feel as though it has gone that far – yet. The cities are relatively calm and there is no sign of a mass armed uprising; just the ongoing control of key sites like airports and communications buildings.
But this peninsula appears to be sliding steadily out of Kiev’s control: the newly-elected Crimean prime minister now says all security and military forces here are under his command and his call to President Putin for direct help will not, says the Kremlin, be ignored. As the new Ukrainian cabinet meets, how to extend its writ here will be the urgent priority.
He was speaking at the first meeting of his cabinet, installed after the overthrow of President Viktor Yanukovych. New Defence Minister Ihor Tenyukh accused Russia of “recently” deploying 6,000 extra soldiers to Ukraine.
US President Barack Obama warned Moscow against any military intervention as unidentified soldiers, thought to be Russian, fanned out in the south of the peninsula, surrounding airports and communications centres.
According to Mr Aksyonov, soldiers from Russia’s Black Sea Fleet based in Crimea are helping to guard strategic buildings.
Under the agreement governing the presence of the fleet in Crimea, the Russians must co-ordinate all troop movements outside the fleet’s base areas with the Ukrainian authorities beforehand. The head of Russia’s upper house of parliament, Valentina Matviyenko, said she could not rule out the dispatch of a “limited contingent” of troops to Crimea to “guarantee the security of the Black Sea Fleet and Russian citizens living on the territory of Crimea”. European Commission President Jose Manuel Barroso has said he is shocked by reports of the “violation of Ukraine’s sovereignty”. Sergiy Aksyonov: “I call on the president of the Russian Federation, Vladimir Putin, to provide assistance in securing peace”
Russia’s foreign ministry said several people had been hurt when “unidentified armed people sent from Kiev” tried to seize control of Crimea’s interior ministry overnight.
The attempt was rebuffed by “self-defence units”, the ministry said in a report which could not be independently confirmed.
According to the Ukrainian news agency Unian, Russian soldiers have been trying to take control of a Ukrainian anti-aircraft missile unit near Yevpatoria, in Crimea.
Mr Aksyonov, who leads the main pro-Russian party in Crimea, was elected prime minister of Crimea by the region’s parliament this week in an emergency session, replacing Anatoliy Mohylyov.
In the same vote, the parliament called a referendum on the status of Crimea, a region dominated by ethnic Russians.
The Crimean prime minister has brought forward the vote to 30 March, from 25 May – the date of Ukraine’s early presidential election.
Mr Aksyonov’s election was not approved by the new authorities in Kiev. Mr Aksyonov has refused to recognise Ukraine’s new government.
He announced he was taking control of security in Crimea “on a temporary basis”.
The new government in Kiev was formed this week by opposition parties and street activists.
Mr Yatsenyuk said: “The presence of Russian soldiers is a provocation and we demand that Russian soldiers return to their permanent bases.”