Russian troops crossed over into Ukraine , Ukrainian Interior Minister Aresn Avakov says . A skirmish ensued , with Ukrainian tanks attacking one column , Avakov says . U.S. officials said in late May that thousands of Russian troops had withdrawn from the border . Russia 's foreign minister tells BBC the claims are false . Ukrainian President talked to Russian President about peace plan , media office says .
Russian troops crossed over into Ukraine , Ukrainian Interior Minister Aresn Avakov says . A skirmish ensued , with Ukrainian tanks attacking one column , Avakov says . Russia 's foreign minister tells BBC the claims are false . Ukrainian President talked to Russian President about peace plan , media office says .