Britian has accused Russian Federation of using a military grade, allegedly Soviet-produced nerve agent belonging to a strain known as Novichok against Sergei and Yulia, both of whom remained in a critical condition.
After three days of threats that Russia's response was coming, Moscow announced on Saturday that it expel 23 diplomats, close the British Consulate-General in St Petersburg and close the British Council in Moscow.
The British diplomats must leave Moscow within a week, Russia's foreign ministry said on Saturday, after a meeting with Britain's ambassador to Russia, Laurie Bristow.
Vladimir Dzhabarov, first deputy of the foreign affairs committee in Russia's upper house of parliament, told Moscow-based Interfax news agency that the British Council was used as a cover organization for British intelligence officers.
British Prime Minister Theresa May this week ordered 23 Russian diplomats expelled as part of measures to punish Russia over the March 4 poisoning of former spy Sergei Skripal and his daughter Yulia in the city of Salisbury. They remain in critical condition in hospital.
Russians voted Sunday in an election set to hand President Vladimir Putin a fourth Kremlin term, as the country is embroiled in a crisis with Britain and its allies over a spy poisoning.More news: Everyone Wins a Free Little Caesar's Lunch Combo Thanks To UMBC
Official London called the incident "indiscriminative and irresponsible attack on the United Kingdom, after which innocent civilians ran the risk", Russian Foreign Ministry considers British accusations a provocation, which disrupts dialogue with Great Britain.
The Russian statement said the government could take further measures if Britain makes any more "unfriendly" moves.
"The onus remains on the Russian state to account for their actions and to comply with their global obligations", it added. "We can be reassured by the strong support we have received from our friends and allies around the world", May said at the Conservative Party's spring forum in London.
On March 13 Russian Foreign Minister Sergei Lavrov says that Moscow is "not guilty" of the poisoning and is ready to cooperate with London.
"Russia's response doesn't change the facts", the spokesperson said. Russia has demanded consular access to Yulia Skripal, a Russian citizen, and complained that Britain has not responded to that request. "Britain is acting too defiantly". It opened offices in Moscow under a 1959 agreement with the Soviet Union and expanded to 15 Russian cities after the 1991 collapse of the Communist state.
Britain said the assistance in that case was not enough, and in 2016, a judge-led inquiry concluded that Putin had probably approved Litvinenko's murder, something Moscow denies. "Relations have been poor for a long time, and the cultural field is the only arena where we can have positive, two-way reciprocal communication".