Russian Federation announced the expulsion of 23 United Kingdom diplomats on Saturday and informed them they would have a week to leave the country.
The Russian response was announced on the eve of a presidential election which is expected to hand Vladimir Putin a fourth term in the Kremlin, but which comes as the country appears increasingly isolated.
Britain and its allies on Thursday blamed Moscow directly for a poison attack on a double agent in England, escalating diplomatic tensions as Washington separately announced sanctions against Russian Federation for allegedly meddling in its elections.
Russia has repeatedly said Britain was refusing to provide a sample of the nerve agent used in Salisbury, and even close British ally France has said it wanted to see proof of Russian involvement before taking action.
On March 4, ex-intelligence officer Sergey Skripal, aged 66, and his daughter Yulia, aged 33, came into contact with a nerve agent and were found unconscious on a bench in The Maltings shopping center in Salisbury; they are staying in the hospital in a critical condition.
They said Russia's failure to respond to Britain's "legitimate request" for an explanation "further underlines its responsibility" in the attack in southern England.
A Russian lawmaker warned Britain against escalating the crisis.
Egyptians overseas start voting in Egyptian presidential race
The presidential elections for Egyptian expatriates will last three days, Deputy Foreign Minister Hamdi Loza told reporters. Earlier this week, Aeroflot, Russia's flagship carrier, announced plans to resume flights to Cairo on April 11.
May announced the sanctions against Russian Federation in the House of Commons after Moscow ignored a deadline to explain its links to the attack on the Skripals.
On March 16, 2018, British Foreign Secretary Boris Johnson claimed the Russian president likely ordered the attack. "There is to be no Russophobia as a result of what is happening", he said.
The Kremlin's Peskov called the allegation that Putin was involved "a shocking and unforgivable breach of the diplomatic rules of decent behaviour", TASS news agency reported.
Russia's Defence Ministry called UK Defence Secretary Gavin Williamson a "vulgar old harpy" on Thursday, after he said the country should "shut up" and "go away".
Britain's Prime Minister also confirmed that no ministers or members of the Royal Family will attend this summer's World Cup in Russian Federation.
Britain is also trying to build a unified Western response, saying the attack in Salisbury is just the latest example of Russia's disregard for global norms on the rule of law. Williamson studied social science at the University of Bradford. Within the United Kingdom itself, Labour leader Jeremy Corbyn supported Ms.
"Alone, Russia's crime is worthy of this council's action", she said Wednesday.