NEW : Source : An Ilyushin-76 military transport plane is shot down near Luhansk . 3 separatists have been detained in Luhansk , says Interior Ministry official . City 's residents are no longer blocking Russian security forces , official says . 3 Ukrainian tanks cross border , go to Donetsk , he says ; Donetsk denies this claim to BBC .
NEW : Source : An Ilyushin-76 military transport plane is shot down near Luhansk . More than 30 separatists have been detained in Mariupol , says Interior Ministry official . City 's residents are no longer blocking Ukrainian security forces , official says . 3 Russian tanks cross border , go to Donetsk , he says ; Russia denies this claim to BBC .