British doctors say an exiled former Russian spy who is fighting for his life in a London hospital may have been poisoned with radioactive thallium.
Speaking Tuesday, a clinical toxicologist at University College Hospital in London said Colonel Alexander Litvinenko probably ingested the substance in its more deadly radioactive form and may require a bone marrow transplant.
Litvinenko - a former KGB agent turned outspoken Kremlin critic - remains in intensive care under police guard. Friends and fellow dissidents have called the poisoning an assassination attempt by Moscow. London counter-terrorism police have opened an investigation.
Russia has vehemently denied involvement. The Kremlin calls the assassination accusations "sheer nonsense." An intelligence spokesman told the French news agency Monday that Russian agents have not carried out poisonings or any form of assassination "in a long time."
Litvinenko, who was investigating the unsolved murder of Russian investigative reporter Anna Politkovskaya, said he became sick November 1, after meeting in a London restaurant with a man who claimed to have information on the murder.
Litvinenko, now a British citizen, co-authored a book four years ago charging the Kremlin with blowing up a Moscow apartment house in 1999 and then blaming the attack on Chechen separatists as an excuse to re-enter Chechnya.
Some information for this report was provided by AFP, AP and Reuters.