The United Kingdom has prolonged a freeze* on the assets of two Russians accused of carrying out the 2006 killing in London of former Federal Security Service officer Aleksandr Litvinenko.

London on January 22 issued the order to freeze the assets of Andrei Lugovoi and Dmitry Kovtun under the terms of the Antiterrorism, Crime, and Security Act of 2001.

On January 21, 2016, Judge Robert Owen, who chaired the British government inquiry into the Litvinenko killing, said he was certain Lugovoi and Kovtun killed Litvinenko by placing a lethal dose of polonium 210 in his tea during a meeting on November 1, 2006.

Litvinenko, who was an outspoken critic of Russian President Vladimir Putin, died several days later.

Both men deny any involvement in Litvinenko's death. However, British investigators found traces of polonium 210 in hotels, restaurants, and aircraft used by Lugovoi. Lugovoi was reportedly treated for radiation poisoning in Moscow in December 2006.

Lugovoi, a former Soviet KGB agent, was elected a member of the Russian State Duma in 2007. Putin awarded him a state medal "for services to the fatherland" in 2015.

*CORRECTION: This story has been amended to clarify that the UK action extended previous asset freeze rather than imposing new sanctions; that Owen made the comment in January 2016, not 2018; and that the medal refers to services to the "fatherland."

With reporting by the BBC