LONDON — A long-awaited public inquiry into the death of Alexander Litvinenko began in London on Tuesday, nine years after the former KGB spy died after drinking tea poisoned with a rare radioactive isotope in the British capital.
From his deathbed, Kremlin-critic Litvinenko, who had been granted British citizenship, accused Russian President Vladimir Putin of ordering his murder and British authorities say there is evidence to charge two ex-KGB agents with murder.
Russia has always denied any involvement in his death.
"The issues to which Mr Litvinenko's death gave rise are of the utmost gravity and have attracted worldwide interest and concern," said chairman Robert Owen at the launch of the inquiry at London's High Court.
British police believe Litvinenko was poisoned with tea laced with the rare isotope polonium-210 at the Pine Bar of the Millennium hotel in central London in November 2006 where he was meeting former Russian spies, Andrei Lugovoi and Dmitry Kovtun.
He died three weeks later. Owen has already said secret British government evidence provided a "prima facie" case of Russian culpability.
Addressing the inquiry, he said the killing had been described as "a miniature nuclear attack on the streets of London" and "state-sponsored assassination by radioactive poisoning".
The controversy generated by the killing chilled Anglo-Russian relations to a post-Cold War low.
As ties improved, Britain rejected holding an inquiry in 2013, admitting the relationship with Russia was a factor although not a decisive one. However, with relations subsequently soured by the Ukraine crisis, the British government changed its mind and gave the go-ahead for the inquiry last July.
Russia has rejected British attempts to extradite Lugovoi and Kovtun, and Owen said they had been invited to give evidence by video link from Russia.
Robin Tam, the lawyer to the inquiry, said Litvinenko had no chance of surviving the amount of polonium he had ingested, and it had led to fears that many thousands of people in London had also been contaminated.
While Litvinenko himself had blamed Russia, there were other theories as to who was behind his death, from the British government and his former friend Russian oligarch Boris Berezovsky to suggestions he had accidentally poisoned himself during an illegal smuggling deal or had even killed himself.
"For some of these theories there is considerable supporting evidence; for others, less, and for yet others, none at all," Tam said.
Litvinenko's wife Marina has said she believes the inquiry will finally shed light on how her husband died, as well as on his work for the British foreign spy agency MI6.