Transcript for Nerve agent that killed former spy, daughter developed in Russia: UK PM

Overseas tonight, and the British government is now puts Russia on notice. Theresa may leaving little doubt that she believes Russia is most likely to blame for the chemical attack against a former Russian spy and his daughter. And there is news tonight on the chemical agent that was used. ABC's chief foreign correspondent Terry Moran on this again tonight. Reporter: Chilling scenes in the quiet English city of Salisbury. Troops donning chemical warfare gear, securing sites contaminated by the nerve agent used to try to kill former Russian spy sergei skripal and his daughter, yuliya. And today, prime minister Theresa may told prlment the weapon was Russian made. It is now clear that Mr skripal and his daughter were poisoned with a military-grade nerve agent of a type developed by Russia. It is highly likely Russia was responsible. Reporter: Called a novichok agent, a next generation chemical weapon up to ten times deadlier than vx or sarin. It attacks the nervous system. Assuming it is Russia, would it have to have been ordered from the top? Yes. There's no way that somebody within the middle ranks could have got their hands on this. It would have had to have come from the very top. Reporter: In Russia, Putin brushed off questions about the attack in Britain. "First, get to the bottom of it there," he said, "Then we'll discuss this." The British government summoned the Russian ambassador today and gave him 24 hours to 'em police station how this advanced chemical weapon came to be used in an assassination attempt in England. David? Terrill Moran, thank you. When we come back tonight,

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