Doctors said Litvinenko was seriously ill after being given the deadly poison thallium -- a toxic metal found in some types of rat poison that can cause damage to the nervous system and organ failure. Such poison has been outlawed in Britain since the 1970s, making it highly unlikely any could have gotten into his food by accident.
Photographs released by the hospital showed a wan Litvinenko in a hospital gown, his bald head propped up by pillows, his arm hooked to an IV drip. Thallium causes hair loss and interferes with the cardiovascular and nervous systems, attacking the vital organs.
Litvinenko's white cell count is down to nearly zero, said Dr. John Henry, a clinical toxicologist treating him. "It shows his bone marrow has been attacked and that he is susceptible to infection," Henry said.
Litvinenko, who has been a thorn in the Russian government's side since the late 1990s, fell ill after a meal with a contact who claimed to have details about the slaying of another Kremlin critic -- Anna Politkovskaya, the Russian investigative journalist who was gunned down Oct. 7 in her Moscow apartment building.
Litvinenko blamed her killing on President Vladimir Putin of Russia.
"Somebody has asked me directly, who is guilty of Anna's death? And I can directly answer you: it is Mr. Putin, president of the Russian Federation," he said at a meeting at a media club in London in October.
Other Russian dissidents in Britain also blamed the Kremlin for Litvinenko's condition.
"Permission to assassinate abroad can only be given from the top," Oleg Gordievsky, former deputy head of the KGB at the Soviet Embassy in London said. "How can it not be state-sponsored?"
"He was for five years attacking Putin and the head of the [secret services] week in, week out. He was deliberately irritating the whole of the Russian establishment, particularly Putin."
In Moscow, Kremlin spokesman Dmitry Peskov dismissed suggestions that Russian intelligence services were involved as "nothing but sheer nonsense."
Alexander Goldfarb, who helped Litvinenko seek asylum in Britain in 2000, said the poison might have been sprinkled into Litvinenko's drink during a meeting at a London hotel Nov. 1 before he went to meet the contact at a sushi restaurant.
Litvinenko joined the KGB counterintelligence forces in 1988, and rose to the rank of colonel in the FSB. He began specializing in terrorism and organized crime in 1991.
