British Prime Minister Theresa May said Britain would consider its next steps alongside its allies in the coming days after Russia had earlier said it would expel 23 British diplomats amid a standoff over a nerve-agent attack on a former spy.
"We will never tolerate a threat to the life of British citizens and others on British soil from the Russian government. We can be reassured by the strong support we have received from our friends and allies around the world," May said on March 17.
The Russian Foreign Ministry said that it will expel 23 diplomats in retaliation after Britain ordered 23 Russian diplomats expelled as part of measures to punish Russia over the poisoning of former spy Sergei Skripal and his daughter in Britain.
Moscow ordered the diplomats to leave within a week.
Escalating a crisis in relations, the ministry also said that it is ordering the closure of the British Council in Russia and canceling an agreement to reopen the British Consulate in St. Petersburg.
The ministry said the measures were a response to what it called Britain's "provocative actions and groundless accusations."
The Foreign Ministry summoned British Ambassador Laurie Bristow in the morning on March 17 to inform him about Moscow’s retaliatory moves.
After the meeting, Bristow told reporters that "this crisis has arisen as a result of an appalling attack in the United Kingdom, the attempted murder of two people, using a chemical weapon developed in Russia and not declared by Russia at the Organization for the Prohibition of Chemical Weapons, as Russia was and is obliged to do under the Chemical Weapons Convention."
Britain's Foreign Ministry said it had anticipated Russia's response and the National Security Council would meet early next week to consider next steps.
"Russia’s response doesn’t change the facts of the matter -- the attempted assassination of two people on British soil, for which there is no alternative conclusion other than that the Russian State was culpable,” the Foreign Office said in a statement.
“The onus remains on the Russian state to account for their actions and to comply with their international obligations,” it added.
The British Council, which promotes cultural ties between the nations, expressed “profound” disappointment over Moscow’s decision to suspend its activities in Russia.
"It is our view that when political or diplomatic relations become difficult, cultural relations and educational opportunities are vital to maintain ongoing dialogue between people and institutions,” it said in a statement on March 17.
Skripal, 66, and his daughter Yulia, 33, were found unconscious on a bench outside a shopping mall in the southern English city of Salisbury on March 4. They remain hospitalized in critical condition.
Britain says Russia was behind what it says was an attempt to kill the Skripals with a powerful chemical substance developed by the Soviet Union.
British officials say they have determined the toxin used in Salisbury was one of a series of nerve agents that were developed in the late Soviet era and are known by the collective name novichok.
Russian Foreign Ministry spokeswoman Maria Zakharova told the Rossia 24 TV channel on March 14 that the most likely source of the substance was Britain itself or the Czech Republic, Slovakia, Sweden, or the United States.
Those countries have been intensively testing the substance since the end of the 1990s, Zakharova asserted.
Swedish Foreign Minister Margot Wallstrom rejected the suggestion that the toxin could have come from Sweden as “unacceptable and unfounded.”
“Russia should answer UK questions instead,” she tweeted.
Czech Defense Minister Karla Slechtova described the suggestion that the toxin could have come from the Czech Republic as "absurd."
And Czech Foreign Minister Martin Stropnicky called the Russian claim "a standard way of manipulating information in the public space through a highly speculative message being introduced which cannot be proven."
On March 16, British Foreign Secretary Boris Johnson accused Russian President Vladimir Putin of personally ordering the poisoning. Putin's spokesman denounced the claim.
“We think it overwhelmingly likely that it was his decision -- to direct the use of a nerve agent on the streets of the U.K., on the streets of Europe for the first time since the Second World War," Johnson said.
In addition to expelling 23 diplomats that May said were spies, she said on May 14 that Britain would suspend all planned high-level bilateral contacts with Russia, revoking an invitation for Russian Foreign Minister Sergei Lavrov to visit, and that British ministers and the royal family would not attend the soccer World Cup in Russia this summer.
Skripal, a retired Russian military intelligence colonel, was convicted of treason in 2006 for passing the identities of Russian intelligence agents to Britain's Secret Intelligence Service, MI6.
He was one of four Russian prisoners released in 2010 in exchange for 10 Russian sleeper agents uncovered in the United States, including Anna Chapman.