British scientists say they are unable to verify that the nerve agent used to poison a former Russian spy and his daughter was made in Russia.
The head of the Porton Down defense research lab said they could only identify the nerve agent as military-grade Novichok, but couldn't pinpoint the source.
He added that establishing its origin required "other inputs", such as intelligence which only the government has access to.
But he did say the methods used to create Novichok were "extremely sophisticated" and was "something only in the capabilities of a state actor".
Russian President Vladimir Putin said he was "bewildered" by the speed at which Prime Minister Theresa May peddled an "anti-Russia campaign."
He also demanded that Russia be part of the investigation into the poisoning into Sergei and Yulia Skripal.
