Russian President Vladimir Putin "probably" personally sanctioned the killing of ex-KGB spy Alexander Litvinenko with radioactive poison in London in 2006, a British judge said Thursday at the conclusion of a public inquiry.

"The FSB (Russian security agency) operation to kill Litvinenko was probably approved by Mr. Patrushev (ex-FSB director) and by President Putin," British judge Robert Owen, the inquiry's chairman, wrote in a 300-page report concluding a six-month probe, according to AFP.

Litvinenko, 43, an outspoken Kremlin critic who is believed to have later worked for MI6, died three weeks after drinking green tea laced with the rare radioactive polonium-210 in London's Millennium Hotel. He had fled Russia for Britain exactly six years before he was poisoned and predicted that Russia would kill him, going on to claim on his deathbed that Putin himself likely ordered the poisoning, NBC News reported.

British police identified former KGB bodyguard Andrei Lugovoy and another Russian, Dmitry Kovtun, as likely culprits, though both deny involvement. Moscow refuses to extradite the men despite international arrest warrants.

"I am sure that Mr. Lugovoy and Mr. Kovtun placed the polonium-210 in the teapot at the Pine Bar on November 1, 2006," Owen said, in what was the first time British authorities directly linked the Russian government to Litvinenko's painful and slow death.

Litvinenko's 44-year-old widow, Marina Litvinenko, welcomed the ruling and said that sanctions should be imposed on Russia and a travel ban on Putin, according to Reuters. "I am of course very pleased that the words my husband spoke on his death bed when he accused Mr. Putin of his murder have been proved true. If you commit this crime, in the end you will face justice," she said. "I'm calling immediately for exclusion from the UK of all Russian intelligence operatives whether from the FSB, who murdered Sasha, or from other Russian agencies based in the London embassy."

Noting that the British government has promised to act, she added: "I'm also calling for the imposition of targeted economic sanctions and travel bans against named individuals."

Russian foreign ministry spokeswoman Maria Zakharova called the findings "politically motivated."

"We had no reason to expect that the final findings of the politically motivated and extremely non-transparent process... would suddenly become objective and unbiased," Zakharova said in a statement.