The British military facility analysing the nerve agent used to poison a Russian spy said on Tuesday it could not prove the substance was made in Russia, as the world's chemical weapons watchdog prepared to hold a meeting at Moscow's request.
Gary Aitkenhead, chief executive of the Porton Down defence laboratory, told Britain's Sky News that analysts had identified the substance as military-grade Novichok, the word used for a category of nerve agents developed in Soviet times. But he added: "We have not identified the precise source".
"It is our job to provide the scientific evidence of what this particular nerve agent is, we identified that it is from this particular family and that it is a military grade, but it is not our job to say where it was manufactured," Aitkenhead said.
He added that "extremely sophisticated methods" were needed to create the nerve agent, and that was "something only in the capabilities of a state actor" Following his remarks, a British Government spokesperson said Porton Down's identification of Novichok was "only one part of the intelligence picture".
"This includes our knowledge that within the last decade, Russia has investigated ways of delivering nerve agents probably for assassination - and as part of this programme has produced and stockpiled small quantities of Novichok; Russia's record of conducting state-sponsored assassinations; and our assessment that Russia views former intelligence officers as targets," it added. Former double agent Sergei Skripal, who has lived in Britain since a spy swap in 2010, and his daughter Yulia have been in hospital since March 4 after the poisoning that London and its major Western allies have blamed on Russia.
The first use of chemical weapons in Europe since World War II has chilled Moscow's relations with the West, as both sides have expelled scores of diplomats.
Britain has also suspended high-level diplomatic contact with Moscow. Moscow has denied any involvement in the incident, with Russian Foreign Minister Sergei Lavrov on Monday suggesting that the British government may be behind the poisoning to distract attention from problems around Brexit.
Aitkenhead would not comment on whether Porton Down had developed or keeps stocks of Novichok, but he dismissed claims the agent used to poison the Skripals had come from the site.