This may be the reason Russia gives for going into Ukraine.
Ukraine’s Defense Ministry says a grenade fired from a launcher caused an explosion in a helicopter at an airfield outside the eastern city of Kramatorsk, wounding a pilot. (April 26)
http://www.youtube.com/watch?v=Y90HzRj4yUw&feature=youtube_gdata
It does seem that the Kiev temporary government is aching for a war instead of an election.