The UK and the European Union have imposed sanctions on several individuals and one organisation following the novichok poisoning of Alexei Navalny.
Six members of Russian government, including the first deputy chief of staff to President Vladimir Putin, Sergei Kiriyenko, and deputy ministers to the ministry of defence, Alexei Krivoruchko and Pavel Popov, have been handed EU and UK travel bans and asset freezes for the foreseeable future.
The sanctions also target the State Scientific Research Institute for Organic Chemistry and Technology in Russia, as well as the director of the federal security service Aleksandr Bortnikov, chief of the presidential domestic policy directorate Andrei Yarin, and Sergei Menyailo, the plenipotentiary representative of the President of the Russian Federation in the Siberian federal district.
EU foreign ministers agreed on Monday to impose the sanctions after a push by France and Germany to freeze the assets and ban the men, who are suspected of being involved in the poisoning, from travelling in Europe to prevent any spread of the toxic nerve agent.
UK foreign secretary Dominic Raab said: "Together with our international partners, we are sanctioning those responsible for the criminal poisoning of Alexei Navalny.
"Any use of chemical weapons by the Russian state violates international law. We are determined to hold those responsible to account."
Mr Navalny, who is a political opponent to President Putin, became ill during a domestic flight in Russia on 20 August.
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He was taken to Germany to be treated and is continuing his recovery there.
After tests by the Organisation for the Prohibition of Chemical Weapons confirmed the nerve agent novichok was used in the poisoning, Russian foreign minister Sergey Lavrov accused Germany of "not planning to provide any facts, despite all international and legal obligations."
He added: "We respond in kind. This is diplomatic practice."
The day before, Mr Lavrov hinted Moscow was considering to sever ties with countries in the West.
He said: "We probably simply have to temporarily stop talking to those people in the West who are responsible for foreign policy and don't understand the need for mutually respectful dialogue."