Fistfights broke out between pro- and anti-Russian demonstrators in Ukraine's strategic Crimea region on Wednesday as Russian President Vladimir Putin ordered massive military exercises just across the border.
The tests of military readiness involve most of the military units in central and western Russia, Defence Minister Sergei Shoigu said in a televised statement. He said the exercise would "check the troops' readiness for action in crisis situations that threaten the nation's military security."
He did not specifically mention the turmoil in Ukraine, which is bitterly divided between pro-European western regions and pro-Russian areas in the east and south.
Three months of protests forced pro-Russian President Viktor Yanukovytch to go into hiding over the weekend as his foes set up an interim government following violent clashes between protesters and police that left more than 80 people dead.
In Crimea's regional capital of Simferopol, about 20,000 Muslim Tatars who rallied in support of the interim government clashed with a smaller pro-Russian rally. A health official said that at least 20 people have been injured.
The protesters shouted and attacked each other with stones, bottles and punches, as police and leaders of both rallies struggled to keep the two groups apart.
The tensions in Crimea — a peninsula in southern Ukraine that is home to Russia's Black Sea Fleet — highlight the divisions that run through this country of 46 million, and underscore fears that the country's mainly Russian-speaking east and south will not recognize the interim authorities' legitimacy.
In Lviv, a major city in the European-leaning west of Ukraine, leading cultural figures tried to defuse the tensions between the Russian-speaking east and the Ukrainian-speaking west, calling on residents to speak only Russian on Wednesday in a symbolic show of solidarity.
The call appeared to have had some effect.
"You can really hear a lot of Russian spoken on the streets of Lviv today," said Konstantin Beglov, one of the campaign's promoters, "although it often leads to funny situations because Lviv residents hardly ever speak Russian."