The chief of the world’s chemical weapons watchdog has said that those responsible for the nerve-agent attack on former Russian double agent Sergei Skripal and his daughter “must be held accountable.” Speaking on Tuesday to the Executive Council of the Organization for the Prohibition of Chemical Weapons, Director-General Ahmet Uzumcu said British Foreign Secretary Boris Johnson called him on Monday evening to inform him about an investigation into the attack, AP reported. British Prime Minister Theresa May had told parliament it was “highly likely” that Russia was to blame for the poisoning with a military-grade nerve agent. Russian Foreign Minister Sergey Lavrov said Moscow had nothing to do with the poisoning. According to Uzumcu, “It is extremely worrying that chemical agents are still being used to harm people. Those found responsible for this use must be held accountable for their actions.”