Alexander Litvinenko, a former Russian spy, died in London on Nov. 23, 2006, after falling ill more than three weeks earlier. The 43-year-old Litvinenko, a fierce Kremlin critic, had blamed Russian President Vladimir Putin for his poisoning from his deathbed. However, British authorities were careful not to blame the Kremlin for his death, despite criticism of Putin's increasing authoritarianism since the poisoning. The Russian government has denied any involvement in Litvinenko's death. Subsequently, traces of radiation were found at a dozen sites in Britain and five jets were being investigated for possible contamination. In Moscow, doctors said they believed Yegor Gaidar, a former premier and head of a liberal opposition party, may have been poisoned during a conference last week in Ireland, his spokesman Valery Natarov told The Associated Press. Gaidar, 50, became violently ill and was rushed to a hospital in Ireland, but was improving in a Moscow hospital. Litvinenko's wife Marina, and three men who met with Litvinenko when he fell ill tested positive for the same radioactive substance that killed him - polonium 210 - but in much smaller doses. After a lengthy investigation by British authorities, On May 22, 2007, British prosecutors accused former KGB agent Andrei Lugovoi of murder in Litvinenko's death and sought his extradition from Russia. The Russian prosecutor-general's office said it would not turn over Lugovoi to British authorities. Credits:  CBS/AP