UK Prime Minister Theresa May has ordered the expulsion of 23 Russian diplomats in retaliation for the poisoning of a former Russian spy and his daughter with nerve agent on British soil, marking the harshest diplomatic action against Russia since the end of the Cold War.

Amid speculation that Russian President Vladimir Putin may have deliberately stoked the crisis as part of his re-election bid, the attention now switches to what retaliation the Kremlin will take against the UK. The Kremlin has dismissed UK accusations of involvement in the attack on former Russian double agent Sergei Skripal.

With Russia-West relations spiralling from bad to worse, this week May said that it was “highly likely” that Russia was behind the poisoning of Skripal.

“There is no alternative conclusion other than that the Russian state was culpable,” May told members of parliament in London.

The prime minister also added that the actions were discussed with the heads of the US, France, and Germany, who supported her position.

The ruble reacted by scaling back its trading gains after the announcement. “[UK Prime Minister Theresa] May spoke of possible freezing of Russian assets, and our oligarchs hold [in the UK] money and real estate, so the ruble reacted negatively," an unnamed trader of a large Western bank told Reuters. 

However, there was no clear guidance on what assets could be blocked. "We will freeze Russian state assets wherever we have evidence that they may be used to threaten the life or property of UK nationals or residents," May said.