Before Litvinenko's death, he wrote a statement accusing the Russian government of his alleged poisoning.
"You have shown yourself to be unworthy of your office. May God forgive you for what you have done. Not only to me. But to all of Russia," read the statement.
The Times, the UK daily, reported that Litvinenko had told Andrei Nekrasov, a friend, before losing consciousness earlier in the week: "The bastards got me. But they won't get everybody."
However, Roger Cox, from the HPA Centre for Radiation, Chemicals and Environmental Hazards, told a central London news conference that a "large quantity" of alpha radiation, "most probably a substance called polonium 210" had been detected in Litvinenko’s urine.
Pat Troop, chief executive of the HPA, said the fact that "someone has apparently been deliberately poisoned by a type of radiation" was an "unprecedented event".
"This man had a high dose of radiation," she added.
Polonium 210 is only dangerous if it is ingested, and a large quantity was detected in his urine, said government experts.
In Helsinki, Vladimir Putin, the Russian president, attended an EU-Russia summit on Friday, and stated that the death has been used to spur political provocation.
"There is no evidence linking the Russian government to the death of Alexander Litvinenko," he said.
|"The bastards got me. But they won't get everybody" |
before he lost consciousness on Tuesday
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Prior to news of the death, a Russian delegation said: "Of course it's a human tragedy. A person was poisoned. But the accusations against the Kremlin are so incredible, so nonsense-like, so silly, that the president cannot comment."
But Oleg Gordievsky, a former colonel in the KGB who defected to Britain in the 1980s, said there was "no doubt" that the Russian secret service was responsible for Litvinenko's death.
Gordievsky told the BBC that he was "very angry that the Russian security service was ... so evil," and described Putin as "an international terrorist".
Father blames Russia
Walter Litvinenko, Alexander's father, laid blame with the Russian government and said: "The [Russian] regime is a mortal danger to the world ... with little morality and no conscience".
At the time of his death, Litvinenko was investigating the recent murder of Russian journalist Anna Politkovskaya.
Politkovskaya - also a vocal critic of Putin - was shot dead at her Moscow flat on October 7.