British Prime Minister Theresa May has said the nerve agent used in an attack on a former Russian spy in a British city has been positively identified as a type manufactured by the Russian Federation, and that the Russian Ambassador to the United Kingdom was summoned Monday.

Describing the poison as a “military grade nerve agent of a type developed by Russia”, Theresa May said the government had given the Russian Federation until the end of Tuesday to explain how the chemical weapon Novichok had come to be used on the streets of Britain.

Remarking that the attack had “caused considerable concern across the community”, the Prime Minister said the British intelligence community had “concluded that it is highly likely that Russia was responsible for the act against Sergei and Julia Skripal” and that it was an “unlawful use of force by the Russian state against the United Kingdom”.

Continuing that there were now only two plausible explanations as to how this might have occurred, May said it would fall to Russia to explain that were it not a direct act of theirs, how a chemical weapon they produced could have got out of control, warning the government was ready to deploy a “full range of appropriate responses” and “Much more extensive measures”.

On summoning the Russian ambassador, May told the House of Commons: “This afternoon my right honourable friend the foreign secretary summoned the Russian Ambassador to the Foreign and Commonwealth Office and asked him to explain… and therefore to account for how this Russian produced nerve agent could have been deployed in Salisbury… the Russian Federation must immediately provide full and complete disclosure of the Novichok programme to the organisation for the prohibition of chemical weapons, and must provide the Russian government’s response by the end of tomorrow”.

May will speak again on Wednesday after considering the Russian response to what she called an “indiscriminate and reckless act against the United Kingdom putting civilians at risk”.

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