Police tracking the would-be killer of business tycoon Boris Berezovsky feared two other London-based Russian dissidents were also assassination targets, The Observer can reveal. Scotland Yard warned the widow of murdered ex-KGB agent Alexander Litvinenko and the exiled Chechen envoy, Akhmed Zakayev, that there was an increased threat to their personal security shortly before the alleged attempt to kill Berezovsky at the Hilton hotel in Mayfair, London, last month. Full Story