ST PETERSBURG, Russia - Russia is concerned that a political vacuum will emerge in Syria if President Bashar Assad leaves power now and that it could be filled by militants, President Vladimir Putin said on Friday."We are concerned about the possible appearance of a political vacuum in Syria if some decisions about a change of government in Syria are taken now," Putin told a joint news conference with German Chancellor Angela Merkel. "Assad goes today, a political vacuum emerges - who will fill it? Maybe ... terrorist organizations."