LONDON, Jan. 21 (UPI) -- A report by the British government that concluded Russian President Vladimir Putin "probably approved" the murder of Alexander Litvinenko, a former spy, has been rejected by Russia's Foreign Ministry.
Litvinenko worked for Russia's Federal Security Service agency before he defected to Britain in 2000 after a series of failed attempts to root out corruption within the FSB and the Russian government. He then became a harsh critic of the Kremlin and an MI6 British intelligence consultant but died in a London hospital in 2006 after being poisoned with the radioactive isotope polonium.
Robert Owen, chairman of Britain's The Litvinenko Inquiry, concluded that Litvinenko was killed by Russians Andrei Lugovoi and Dmitry Kovtun on orders from former FSB chief Nikolai Patrushev, which Putin may have authorized.
"Taking full account of all the evidence and analysis available to me I find that the FSB operation to kill Litvinenko was probably approved by Mr. Patrushev and also by President Putin," Sir Owen writes in the report.
Russia's Foreign Ministry said the report was "politically motivated."
"We regret that a purely criminal case has been politicized and has darkened the general atmosphere of our bilateral relations," the ministry said.
Lugovoi, a prime suspect, dismissed the report as "absurd," adding that "the results released today just show London's anti-Russian position once again."
International arrest warrants are still in place for suspects Lugovoi and Kovtun, while British Home Secretary Theresa May announced the Treasury Ministry would freeze the suspect's assets.
"The conclusion that the Russian state was probably involved in the murder of Mr. Litvinenko is deeply disturbing," May said in a statement. "It goes without saying that this was a blatant and unacceptable breach of the most fundamental tenets of international law and of civilized behavior."
Lugovoi, currently a member of the Russian parliament, was given an award by Putin in 2015 for his "services to the fatherland."
Litvinenko's widow, Marina, welcomed the report's findings and urged for action to be taken.
"I am pleased that the words that my husband spoke on his deathbed when he accused Mr. Putin his murder has been proved through an English court with a high standard of independence and fairness but now it's time for David Cameron. I'm calling immediately for expulsion from the U.K. of all Russian intelligence operatives," Marina Litvinenko told reporters. "I'm also calling for the imposition of targeted economic sanctions and travel bans against named individuals including Mr. Patrushev and Mr. Putin."