Russian tanks crossed border into Ukraine , Ukrainian Interior Minister Aresn Avakov says . Western leaders have accused Moscow of fomenting instability in eastern Ukraine . A skirmish resulted , with Ukrainian forces attacking one column , Avakov says . - The U.S. State Department has warned Americans in Crimea to leave the peninsula and return home immediately because of a possible threat from Russia. Ukrainian President talked to Russian leader about peace plan , media office says .
Russian tanks crossed border into Ukraine , Ukrainian Interior Minister Aresn Avakov says . A skirmish resulted , with Ukrainian forces attacking one column , Avakov says . - The U.S. State Department has warned Americans in Crimea to leave the peninsula and return home immediately because of a possible threat from Russia. Ukrainian President talked to Russian leader about peace plan , media office says .