Russian President Vladimir Putin ordered an urgent drill to test the combat readiness of the armed forces across western Russia on Wednesday, news agencies reported, flexing Moscow's military muscle amid tension with the West over Ukraine.
"In accordance with an order from the president of the Russian Federation, forces of the Western Military District were put on alert at 1400 (1000 GMT) today," Interfax quoted Defense Minister Sergei Shoigu as saying.
Putin has ordered several such surprise drills in various parts of Russia since he returned to the presidency in 2012, saying the military must be kept on its toes, but the geopolitical overtones could hardly have been clearer this time.
The western district borders Ukraine, which lies between NATO nations and Russia. Shoigu said the drill would be conducted in two stages, ending on March 3, and also involved some forces in central Russia.
Putin has made no public comment on Ukraine since Yanukovych was driven from power.
The United States and European nations have warned Russia against military intervention in Ukraine, a former Soviet republic that Putin has called a "brother nation" and wants to be part of a Eurasian Union he is building in the region.
On Tuesday, a Russian lawmaker visiting Crimea said Moscow would protect the region's Russian-speaking residents, raising concern that Russia could be trying to justify military action.
Valentina Matvienko, speaker of the Federation Council, the upper chamber of the Russian parliament, on Wednesday dismissed claims that Russia could conduct a military operation in Ukraine. "That scenario is impossible," she said.
"Russia has been stating and reiterating its stance that we have no right and cannot interfere in domestic affairs of a sovereign state," said Matvienko, a close Putin ally who was born in western Ukraine. "We are for Ukraine as a united state, and there should be no basis for separatist sentiments."
But Prime Minister Dmitry Medvedev said on Monday that Russia's interests and its citizens in Ukraine were under threat, language reminiscent of statements justifying Russia's invasion of Georgia in 2008, when he was president.
Rival groups clash in Crimea
Meanwhile, one man died of a heart attack Wednesday and 20 were injured in fistfights as pro-Russian demonstrators brawled with supporters of Ukraine's new interim authorities in the capital of the Russophone Crimea peninsula Simferopol, the region's health ministry said, AP reported.
Over 10,000 Crimean Tatars rallied in support of Ukraine's interim leaders, waving Ukrainian flags and chanting "Ukraine is not Russia," while a smaller pro-Russian rally nearby called for stronger ties with Russia and waving Russian flags.
Police and leaders from both sides were struggling to keep the two groups apart, as protesters shouted and punched each other in ongoing scuffles.
The tensions in Crimea - a peninsula jutting into the Black Sea that is strategically critical region because it is home to Russia's Black Sea Fleet - highlight the divisions that run through this country of 46 million after months of protests that ultimately forced the pro- Russia President Viktor Yanukovych to flee the capital. It also underscores fears that the country's mainly Russian-speaking east will not recognize the interim authorities' legitimacy.
Crimean Tatars took an active part in the protest movement against Yanukovych and harbor deep resentment against the Kremlin, having been deported en masse on the orders of Soviet dictator Josef Stalin during the World War II.
"We will not let the fate of our land to be decided without us," said Nuridin Seytablaev, 54, an engineer. "We are ready to fight for Ukraine and our European future."
Nearby, separated by police lines, Anton Lyakhov, 52, waved a Russian flag. "Only Russian can defend us from fascists in Kiev and from Islamic radicals in Crimea."