E.U. Court Rules Russia was Behind 2006 Assassination in the U.K.

The European Court of Human Rights ruled on Tuesday that Russia was responsible for the 2006 killing of Alexander V. Litvinenko, who was poisoned to death with a deadly toxin at a London hotel.

The ruling concluded thatthe assassins were acting as “agents of the Russian state,” bolstering a separate inquiry by Britain that found “strong circumstantial evidence” that President Vladimir V. Putin of Russia and his spy chief at the time, Nikolai Patrushev, had approved an operation to kill Mr. Litvinenko, using a highly toxic and rare isotope, polonium 210.

Mr. Litvinenko was a former colonel in the F.S.B., the domestic successor to the Soviet-era K.G.B., who fled Russia via Georgia and Turkey in 2000 to seek asylum in Britain, where he became a whistle-blower and a vitriolic critic of Mr. Putin.

He died in November 2006, weeks after drinking green tea laced with polonium-210 at London’s Millennium Hotel.

A lengthy British inquiry concluded in 2016 that Andrei K. Lugovoi, a former K.G.B. bodyguard, and Dmitri V. Kovtun, a Red Army deserter, poisoned Mr. Litvinenko.

While the 328-page report was scathing, it cited no hard evidence that Mr. Putin or Mr. Patrushev had been aware of the plot to kill Mr. Litvinenko or had sanctioned it.

Russia has denied any involvement in the murder of Mr. Litvinenko.