We're going to hear more now about the public inquiry of a Russian dissident in London nearly 10 years ago.
The report from a judge in Britain is more than 300 pages long, and it says Russia's president probably approved the killing.
NPR's Leila Fadel begins our coverage from London.
LEILA FADEL, BYLINE: On his deathbed, Alexander Litvinenko dictated a statement accusing Russia's president, Vladimir Putin, of poisoning him.
After he passed away, it was read to the press by his friend Alexander Goldfarb.
ALEXANDER GOLDFARB: May God forgive you for what you have done not only to me but to beloved Russia and its people.
FADEL: Today, Litvinenko's widow, Marina, said her husband had been proven right.
MARINA LITVINENKO: The words my husband spoke on his deathbed when he accused Mr. Putin of his murder have been proved through an English court.
FADEL: The report says that in 2006, Litvenenko was poisoned in a West London hotel with a cup of green tea laced with radioactive polonium 210,
an isotope manufactured in a nuclear reactor, the kind only a state could get its hand on,
so radioactive that Litvinenko was buried in a lead-lined coffin.
He'd been an outspoken critic of the Kremlin and of President Vladimir Putin and was said to be working with Britain's intelligence service.
The report's author, retired judge Robert Owen, said Litvinenko was killed by two men — Andrei Lugovoi and Dmitri Kovtun.
ROBERT OWEN: There is no evidence to suggest that either had any personal reason to kill Mr. Litvinenko.
All the evidence points in one direction, namely that then when they killed Mr. Litvinenko, they were acting on behalf of someone else.
FADEL: That someone else was the head of Russian intelligence at the time, Nikolai Patrushev,
and Judge Owen said the murder was probably done with the approval of Vladimir Putin.
Litvinenko's widow called for action by Prime Minister David Cameron.
LITVINENKO: I'm calling immediately for expulsion from the U.K. of all Russian intelligence operatives.
I'm also calling for the imposition of targeted economic sanctions and travel bans against named individuals.
FADEL: Including, she said, the Russian president. British Home Secretary Theresa May addressed parliament soon after the report was released.
THERESA MAY: It goes without saying that this was a blatant and unacceptable breach of the most fundamental tenets of international law and of civilized behavior.
FADEL: She called for the extradition of the two alleged assassins from Russia and said international arrest warrants have already been issued.
May said the U.K. Treasury is freezing their assets in Britain, but she made no mention of any new specific sanctions on Putin or other officials on top of the already existing sanctions on Russia over its seizure of Ukraine.
MAY: We will continue to engage guardedly with Russia where it is strictly necessary to do so to support the U.K.'s national interest.
FADEL: The British government has asked Russia to cooperate with the criminal investigation into Litvenenko's death and account for the actions of its intelligence services. Leila Fadel, NPR News, London.