Russian Federation confirmed Friday it will expel British diplomats and halt high-level meetings in turn.
The UK Government has said it is "highly likely" that Russian Federation was behind the attack but until now has not directly suggested Mr Putin was personally responsible for ordering the poisoning, which used the "military grade" nerve agent Novichok.
Former spy Sergei Skripal and his daughter, Yulia, were found unconscious on a park bench in the English town of Salisbury and rushed to the hospital, where they remain in serious condition.
She described the expulsion of Russian diplomats from Britain as "a just response". There has been much talk in Moscow of imminent and decisive retaliation, but so far nothing of substance has taken place.
The PM, who also met Public Health England officials, expelled the Russian diplomats on Wednesday after Moscow refused to meet the UK's deadline to explain the use of the nerve agent. In a separate action, the Trump administration issued sanctions on a number of Russian entities for a wide range of behavior, including attempts to interfere in the 2016 presidential election.
The demand was rejected and, on Wednesday, the United Kingdom imposed sanctions on Russia, which included expelling 23 diplomats, limiting diplomatic ties, and freezing Russian state assets in the UK. "Those [American] politicians are playing with fire", he said.
Britain has said the toxin was Novichok, a lethal nerve agent first developed by the Soviet military.
The gulf between Russia and Britain widened on Friday as they cranked up pressure over a nerve agent attack and a suspected murder in Britain that have deepened Western worries about alleged Russian meddling overseas. "There is to be no Russophobia as a result of what is happening", he said.
Meanwhile, the Kremlin expressed its surprise by Britain's behavior towards Russian Federation, the United Kingdom's position in relation to the poisoning of former GRU Colonel Sergei Skripal because it contradicts worldwide law and common sense, according to Kremlin spokesman Dmitry Peskov.
"All the investigation about the Skripals is classified", he told RT. Several other individuals, including a police officer, were sickened.
Writing in the Guardian on Friday, opposition Labour Party leader Jeremy Corbyn called for "calm heads" and warned against rushing into a "new cold war".
Some scientists say it's feasible that the nerve agent could be made stable enough to travel and that various compounds could have been added to Novichok to make it a clear, colorless liquid resembling water, perfume or alcohol. "In my years in parliament I have seen clear thinking in an global crisis overwhelmed by emotion and hasty judgments too many times", he wrote.
Russian Federation also suspects foul play in Glushkov's death and opened its own inquiry Friday. The wealthiest snap up London's luxury homes for eye-popping prices. "We want to clarify all the questions behind this provocation - this is exactly how we see [this incident]", he added. You get used to situations when you don't feel comfortable and when you don't know what will happen. She said it was part of a "well established pattern" of Russian actions.
"That is why we are at odds with Russian Federation". "The U.K. has leverage there".
After the first known offensive use of such a weapon in Europe since World War II, May pointed the finger squarely at President Vladimir Putin and gave the 23 Russians, who she said were spies working under diplomatic cover at the London embassy a week to leave.
The leaders did not say what, if any, actions they would take if Russian Federation does not comply.
US President Trump's spokeswoman accused Russian Federation of undermining the security of countries worldwide.