The deadly poisoning of a former Russian spy in London a decade ago was "probably approved" by Vladimir Putin, according to a judicial report released Thursday, a conclusion that confirmed long-held suspicions that the high-profile case bore all the hallmarks of a Kremlin hit.

The Kremlin fired back, saying the report could "still further poison the atmosphere of our bilateral relations."

Alexander Litvinenko, who had turned on his former KGB colleague Putin, died three weeks after drinking tea laced with polonium-210 at a London hotel in November 2006. The cause of death was acute radiation syndrome, and his rapid decline touched off a frantic effort to find out if anyone else in the British capital was exposed to the deadly toxin.

There is a "strong possibility" that Russia's FSB security service, the successor agency to the notorious KGB, directed the killing, Judge Robert Owen wrote in his 326-page report. And the rubout would not have occurred without the likely approval of not only then-FSB head Nikolai Patrushev, but also Putin himself, the report stated.

The report named Russian politicians Andrei Lugovoi and Dmitry Kovtun as the suspects who carried out the poisoning. Both returned to Russia.

Andrei Lugovoi, left, and Dmitry Kovtun in 2007. (AP Photo/Sergey Ponomarev, File)

Putin even rewarded Lugovoi last year with a medal for "services to the motherland," recognizing "courage and bravery displayed in the performance of his professional duty under conditions fraught with risk for his life." An attorney for Litvinenko's widow called it "the clearest possible message" Putin sided with Lugovoi.

Moscow has long denied a role in the murder of Litvinenko, who "had repeatedly targeted President Putin" with "highly personal" public criticism and charges of corruption, the report noted. Litvinenko had fled to Great Britain in 2000 and was granted asylum after breaking with Putin and his inner circle.

From his hospital bed, Litvinenko, who was 44, pointed a dying finger at Putin, but the new report marks the first time the Russian president has been officially linked to the killing.

"There can be no doubt that Alexander Litvinenko was poisoned by Mr. Lugovoi and Mr. Kovtun."
— Judge Robert Owen's report

Litvinenko's widow, Marina, said outside the High Court Thursday that she was "very pleased that the words my husband spoke on his deathbed when he accused Mr. Putin have been proved by an English court."

She called for British Prime Minister David Cameron to take urgent steps against Russian agents operating inside Britain in light of the report.

"I'm calling immediately for expulsion from the UK of all Russian intelligence operatives ... based at the London embassy," she said. "I'm also calling for the imposition of targeted economic sanctions and travel bans against named individuals including Mr. (former FSB chief Nikolai) Patrushev and Mr. Putin."

She said Britain's Home Office had written to her Wednesday night promising action. Home Secretary Theresa May, who is in charge of justice issues, said the British government would freeze the assets of Lugovoi and Kovtun.

Lugovoi is a member of the Russian parliament, which means he is immune from prosecution. In an interview with the Interfax news agency, he called the charges against him "absurd."

"As we expected, there was no sensation," he said. "The results of the investigation that were announced today once again confirm London's anti-Russian position and the blinkered view and unwillingness of the British to establish the true cause of Litvinenko's death."

Russian Foreign Ministry spokeswoman Maria Zhakarova said Thursday that the government does not consider Owen's conclusions to be objective or impartial.

"We regret that a purely criminal case has been politicized and has darkened the general atmosphere of bilateral relations," Zhakarova said in a statement. She said Britain's decision to hold a public inquiry on the case was politically motivated and that the process was not transparent for the Russian side or the public.

The British government appointed Owen to head a public inquiry into the slaying, which soured relations between London and Moscow. He heard from dozens of witnesses during months of public hearings last year, and also saw secret British intelligence evidence.

Announcing his findings at London's Royal Courts of Justice, Owen said that "there can be no doubt that Alexander Litvinenko was poisoned by Mr. Lugovoi and Mr. Kovtun" in the Pine Bar of London's luxury Millennium Hotel on Nov. 1, 2006. He also charged that the pair had failed in an attempt to poison Litvinenko weeks earlier.

Just last year, Kremlin involvement was suspected in the murder of an outspoken Putin critic in Russia and the near-fatal poisoning of another.

Boris Nemtsov was gunned down last February as he strolled near the Kremlin with a woman, and a close friend of his, Vladimir Kara-Murza Jr., a Washington resident who was in a hotel in Moscow when he suddenly lost consciousness May 26, was hospitalized with what his wife called "symptoms of poisoning."

Kara-Murza, who recovered, is a coordinator for Open Russia, a nongovernmental organization and had on the previous day released a documentary film accusing close Putin crony and Chechen strongman Ramzan Kadyrov of human rights abuses including torture and murder.

The Associated Press contributed to this report.