The U.K. has called for an urgent meeting of the UN Security Council on the investigation of the nerve agent attack in Salisbury, said a statement from the Foreign and Commonwealth Office Wednesday.
The call for the meeting came after Russia missed a deadline by London to explain how a certain type of military-grade nerve agent was used in the attack targeting ex-Russian spy Sergei Skripal on March 4.
British Prime Minister Theresa May is expected to announce a series of measures against Russia Wednesday afternoon.
Moscow repeatedly said it has "no motive" in the attempted murder of Skripal and his daughter Yulia.
The British Foreign Office said the incident in Salisbury "follows a well-established pattern of Russian state aggression".
Sergei Skripal, 66, and his daughter Yulia, 33, were admitted to a hospital after being found unconscious on March 4 in the southern English city of Salisbury.
"It is now clear that Mr. Skripal and his daughter were poisoned with a military-grade nerve agent of a type developed by Russia," specifically from the Novichok group, May told British lawmakers on Monday.
The incident has drawn comparisons to the fate of former KGB agent Alexander Litvinenko, who died in 2006 after drinking radioactive tea. Former KGB bodyguards identified as suspects in the murder denied any involvement.
Skripal was granted refuge in the U.K. following a 2010 spy exchange between the U.S. and Russia. Convicted by a Moscow military court of "high treason" after admitting to leaking information to British intelligence, he had been sentenced to 13 years in prison.
