British ambassador to Russia, Laurie Bristow, arrives for a meeting at the Russian foreign ministry building in Moscow, Russia, Saturday, March 17, 2018. Russia's Foreign Ministry has summoned Bristow for talks in a heightening dispute over a nerve agent attack on a former spy in Britain. Russia is expected to announce the expulsion of some British diplomats in a retaliatory measure. (AP Photo/Pavel Golovkin)
British ambassador to Russia, Laurie Bristow, arrives for a meeting at the Russian foreign ministry building in Moscow, Russia, Saturday, March 17, 2018. Russia's Foreign Ministry has summoned Bristow for talks in a heightening dispute over a nerve agent attack on a former spy in Britain. Russia is expected to announce the expulsion of some British diplomats in a retaliatory measure. (AP Photo/Pavel Golovkin) Credit: Pavel Golovkin

Russia on Saturday announced it is expelling 23 British diplomats and threatened further measures in retaliation in a growing diplomatic dispute over a nerve agent attack on a former spy in Britain.

The Russian Foreign Ministry also said in a statement that it is ordering the closure of the British Council, a government organization for cultural and scientific cooperation, and that it is ending an agreement to reopen the British consulate in St. Petersburg.

It ordered the diplomats to leave within a week.

The announcement followed on the heels of Britain’s order this week for 23 Russian diplomats to leave the U.K. because Russia was not cooperating in the case of Sergei Skripal and his daughter, both found March 4 poisoned by a nerve agent that British officials say was developed in Russia. The Skripals remain in critical condition.

Britain’s foreign secretary accused Russian President Vladimir Putin of personally ordering the poisoning of the Skripals. Putin’s spokesman denounced the claim.

The Russian statement said the government could take further measures if Britain takes any more “unfriendly” moves toward Russia. British Ambassador Laurie Bristow was called to the Foreign Ministry Saturday morning to be informed of the moves.

“We will always do what is necessary to defend ourselves, our allies and our values against an attack of this sort, which is an attack not only on the United Kingdom, but upon the international rules-based system on which all countries, including Russia, depend for their safety and security,” Bristow told reporters after being informed of the expulsions.”

British Prime Minister Theresa May is seeking a global coalition of countries to punish Moscow.