The Organisation for the Prohibition of Chemical Weapons (OPCW) has backed the UK's identification of the nerve agent used in Salisbury last month.
Without naming the substance, their executive summary stated: “The results of the analysis by the OPCW designated laboratories of environmental and biomedical samples collected by the OPCW team confirms the findings of the United Kingdom relating to the identity of the toxic chemical that was used in Salisbury and severely injured three people.”
An analysis of environmental samples taken from the scene, and blood samples taken from ex-Russian spy Sergei Skripal, 66, his 33-year-old daughter Yulia, and Detective Sergeant Nick Bailey, who was also injured, allowed them to draw this conclusion.
The text added that the toxic chemical was of "high purity", and its name and structure has been contained in a "classified report" available to state members of the OPCW.
Sergei and Yulia Skripal were found slumped on a park bench in Salisbury on March 4. It was later found that they were poisoned by a nerve agent.
The UK and its western allies say Russia was behind the attack, while Moscow has denied wrongdoing.
'No one speaks for me'
The chemical watchdog's announcement follows Yulia's statement on Wednesday, when she rejected the Russian embassy's help "for now" — and said "no one speaks for me" after being discharged from hospital.
"I am safe and feeling better as time goes by, but I am not yet strong enough to give a full interview to the media, as I one day hope to do," she continued.
"Until that time, I want to stress that no one speaks for me or for my father, but ourselves.
"I have left my father in their care, and he is still seriously ill. I too am still suffering with the effects of the nerve agent used against us."
After her comments were released by the Metropolitan Police, the Russian embassy was sceptical, saying: "We continue to insist on a meeting with Yulia and Sergei Skripal. The situation around them looks more and more like a forceful detention or imprisonment."
Yulia was discharged from a Salisbury hospital on Monday.
The Skripals were in a critical condition for weeks after the attack before their health improved.
Sergei, who was recruited by Britain's intelligence agency MI6, was arrested for treason in Moscow in 2004. He ended up in Britain after being swapped in 2010 for Russian spies caught in the United States.