The EU has recalled its ambassador to Moscow for what it describes as "consultations” following the nerve agent attack in the UK.
Member states have agreed they view it as "highly likely" that Russia is responsible for the Salisbury attack.
Last night, European Council President Donald Tusk revealed the bloc's member states have backed the UK Government's assessment that there is "no other plausible explanation" than Moscow's culpability.
Former double agent Sergei Skipral and his daughter Yulia remain under heavy sedation in hospital nearly three weeks after being found unconscious on a bench in the south England town.
Their condition is described as critical but stable.
Meanwhile the British police officer who was injured in the attack has been discharged from hospital - and says his life "will never be the same again."
Following a working dinner at a Brussels summit on Thursday, EC President Donald Tusk posted on twitter: "#EUCO agrees with UK government that highly likely Russia is responsible for #SalisburyAttack and that there is no other plausible explanation."
In response The British Prime Minister Theresa May said she welcomed the fact that the European Council is "standing together" over the incident adding that "the threat that Russia poses respects no borders and it is a threat to our values."
The EU decision to recall its ambassador to Moscow "for consultations" is not a formal sanction.
Reports suggest that as many as five EU countries - France, Poland and the three Baltic states - could now follow Britain's lead by expelling suspected Russian diplomats.
Mrs May held a trilateral meeting with the leaders of France and Germany on the sidelines of the EU summit before running the rest f the leaders through the latest on Salisbury over dinner.
Both Emanuel Macron and Angela Merkel reaffirmed their agreement that the Russian state must have been involved in the attack.
"The leaders agreed on the importance of sending a strong European message in response to Russia's actions and agreed to remain in close contact in coming days," said a spokesperson for Mrs May.
Earlier on Thursday, Russia's ambassador to the UK, Alexander Yakovenko, claimed EU countries were awaiting evidence from Britain over the Salisbury attack.
"Basically I think all the countries of the EU will be happy to see something before they make conclusions," he said.
"What I was told by one ambassador yesterday was first we want to see the evidence, then to make conclusions."
Mr Yakovenko's comments came as a UK judge ruled doctors will be able to take blood samples from the Skripals to send to experts at international watchdog, the Organisation for the Prohibition of Chemical Weapons.
The court ruling also revealed medical tests indicate the Skripals "mental capacity might be compromised to an unknown and so far unascertained degree" as they remain in an unconscious condition in hospital.
