The Organisation for the Prohibition of Chemical Weapons (OPCW) confirmed Tuesday that it was the Soviet-developed Novichok nerve agent that poisoned a British couple in southern England earlier this year.
Dawn Sturgess, a 44-year-old mother of three, died on July 8 after being exposed to the poison contained in a perfume bottle that her partner Charlie Rowley had given her.
Rowley, who recovered from the attack, returned to hospital last month with eye trouble.
Police initially thought the couple had consumed contaminated drugs but tests carried out at a defence laboratory near Salisbury determined the substance was Novichok, a military-grade nerve agent developed by the Soviet Union during the Cold War.
The OPCW has now confirmed that finding.
The results of the Hague-based body's analysis "confirm the findings of the United Kingdom relating to the identity of the toxic chemical that intoxicated two individuals in Amesbury and resulted in one fatality," the OPCW said in a statement.
"This was a Novichok nerve agent, of the same kind used in the attempted assassinations of Sergei and Yulia Skripal earlier this year," it added.
London has blamed the March poisoning in southwestern England of former Russian double agent Sergei Skripal and his daughter Yulia on Moscow, plunging the two countries into a diplomatic crisis.
Russia denies any involvement but the row has led to tit-for-tat expulsions of diplomats between Britain and its allies on one side and Russia on the other.
“We are grateful to the OPCW for the independent, expert work in confirming the type of nerve agent used in Amesbury," Britain's Foreign Secretary Jeremy Hunt said in a statement.
“The recklessness of the Russian state in bringing a nerve agent in to the UK, and total disregard for the safety of the public, is appalling and irresponsible," he added.