LONDON -- A former Russian spy who said he had been poisoned died last night in an intensive care unit, and doctors were unable to pinpoint the cause of death, officials with London's University College Hospital said.
Alexander Litvinenko, a fierce critic of the Russian government, had suffered heart failure and was heavily sedated as medical staff struggled to determine what had made the 43-year-old critically ill.
The former spy said he believed he had been poisoned on Nov. 1 while investigating the slaying of another Kremlin detractor -- investigative journalist Anna Politkovskaya. His hair fell out, his throat became swollen, and his immune and nervous systems were severely damaged, he said.
Doctors said tests had virtually ruled out poisoning by thallium and radiation -- toxins once considered possible factors in his sickness.
Friends and dissidents allege the poisoning was carried out at the behest of the Russian government. Litvinenko sought asylum in Britain in 2000, and has been a relentless critic of the Kremlin and the Russian security services ever since. The Russian Foreign Intelligence Service said it was not involved in any murder attempt.
On the day he first felt ill, Litvinenko said, he had met at a London hotel with an unidentified Russian and with Andrei Lugovoy, a former KGB colleague and bodyguard to onetime Russian prime minister Yegor Gaidar .