Britain will expel 23 Russian diplomats as part of a package of measures against Moscow, which ignored a midnight deadline to explain how a nerve agent developed during the Cold War was used to poison a former Russian spy in Britain.
Prime Minister Theresa May told lawmakers on March 14 that the diplomats will have one week to leave the country, saying they were identified as "undeclared intelligence officers."
May said there is "no alternative conclusion, other than that the Russian state was culpable for the attempted murder" of former double agent Sergei Skripal, 66, and his daughter Yulia, 33.
May said that the move, described as the biggest expulsion of Russian diplomats from Britain in 30 years, will degrade Russian intelligence capabilities in Britain for years to come.
She also said that Britain will suspend all planned high-level bilateral contacts with Russia, revoking an invitation for Foreign Minister Sergei Lavrov to visit, and that British ministers and the royal family will not attend the soccer World Cup in Russia this summer.
"We will freeze Russian state assets wherever we have the evidence that they may be used to threaten the life or property of U.K. nationals or residents," May also announced.
The United States, European Union, and NATO all voiced support for Britain after May said a day earlier that it was "highly likely" that Russia was behind the poisoning of the former double agent and his daughter.
British authorities say the two were exposed to a deadly chemical substance developed by the Soviet military that was part of a group of nerve agents known as Novichok. They are treating it as a case of attempted murder.
The Skripals remained in critical condition 10 days after they were found unconscious on a bench outside a shopping mall in the southern city of Salisbury.
May had given Moscow a deadline of midnight on March 13 to explain how the rare nerve agent made its way to England.
Russia has denied involvement and ignored the deadline, with Lavrov saying that Moscow is "not guilty" and that Britain was not following the proper procedures for reporting suspected chemical weapons attacks
Britain has called for an urgent meeting of the UN Security Council -- on which both Russia and Britain hold permanent seats -- to update members on the investigation into the poisoning, the Foreign Office said.
With reporting by Sky News, AFP, AP, Reuters, and Sky News