The UK will expel 23 Russian diplomats following a nerve agent attack on a former Russian double agent in Southern England.
Prime Minister Theresa May said the diplomats, who were “undeclared intelligence officers”, had a week to leave in what was the single biggest expulsion in more than 30 years.
Britain would also freeze Russian state assets wherever there was evidence of a threat and introduce new measures to strengthen defences against “hostile state activity”.
No ministers or members of the British royal family would also attend the soccer World Cup in Russia.
“They have treated the use of a military-grade nerve agent in Europe with sarcasm, contempt and defiance,” May said in parliament.
It came after former spy Sergei Skripal, 66, and his daughter Yulia, 33 were found unconscious on a bench outside a shopping centre in Salibury on March 4, after they were poisoned.
They remain in hospital in a critical condition.
A police officer was also harmed and remains in a serious condition.
Ms May said it was clear Russia was responsible for the attack using Novichok, a Soviet-era military-grade nerve agent.
She had asked Moscow to explain if it was responsible for the attack or if it had lost control of its inventory of the substance.
“Their response demonstrated complete disdain for the gravity of these events,” Ms May said.
“There is no alternative conclusion other than that the Russian state was culpable for the attempted murder of Mr Skripal and his daughter, and for threatening the lives of other British citizens in Salisbury.”
“This represents an unlawful use of force by the Russian state against the United Kingdom.
Russia responded on Wednesday, denying any involvement and called the UK’s move “an unprecedently crude provocation”
They warned Britain to expect retaliation.