BBC News
April 2003 - Liberal politician Sergey Yushenkov assassinated near his Moscow home July 2003 - Investigative journalist Yuri Shchekochikhin died after 16-day mysterious illness
July 2004 - Forbes magazine Russian editor Paul Klebnikov shot from moving car on Moscow street, died later in hospital
October 2006 - Investigative journalist Anna Politkovskaya shot dead outside her Moscow apartment
November 2006 - Former Russian spy Alexander Litvinenko died nearly three weeks after drinking tea laced with polonium in London hotel
March 2013 -Boris Berezovsky, former Kremlin power broker turned Putin critic, found dead in his UK home