UK military research boss can't say whether nerve agent was Russian

However, he confirmed the substance required "extremely sophisticated methods to create, something only in the capabilities of a state actor".

The head of Britain's military research centre said on Tuesday it was unable yet to say whether the military-grade nerve agent that poisoned a Russian double-agent last month had been produced in Russia.

"We were able to identify it as Novichok, to identify that it was military-grade nerve agent," Gary Aitkenhead, chief executive of the Defence Science and Technology Laboratory at Porton Down in England, told Sky News.

"We have not identified the precise source, but we have provided the scientific info to government who have then used a number of other sources to piece together the conclusions you have come to."

However,