Litvinenko, 43, an outspoken critic of Putin who fled Russia, died after drinking green tea laced with the rare radioactive isotope polonium-210 at London's plush Millennium Hotel.
 
An inquiry led by senior judge Robert Owen found that former KGB bodyguard Andrei Lugovoy and fellow Russian Dmitry Kovtun carried out the poisoning as part of an operation directed by Russia's Federal Security Service (FSB), the main heir to the Soviet-era KGB.

"Taking full account of all the evidence and analysis available to me, I find that the FSB operation to kill Mr Litvinenko was probably approved by Mr Patrushev and also by President Putin," the inquiry said.

Nikolai Patrushev was formerly head of the FSB. "I am satisfied that in general terms members of the Putin administration, including the President himself and the FSB, had motives for taking action against Mr Litvinenko, including killing him in late 2006," the inquiry said.

The Kremlin has always denied any involvement. From his deathbed, Litvinenko told detectives Putin had directly ordered his killing.

The death of Litvinenko marked a post-Cold War low point in Anglo-Russian relations, and ties have never recovered, marred further by Russia's annexation of Crimea and its support for Syrian President Bashar al-Assad.

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