This is an image of the daughter of former Russian Spy Sergei Skripal, Yulia Skripal taken from Yulia Skipal's Facebook account on Tuesday March 6, 2018. Britain's Foreign Office says it has asked the Organization for the Prohibition of Chemical Weapons to publish a summary of its findings at midday on Thursday April 12, 2018, on the nerve agent used to poison a former spy and his daughter in southwestern England.(Yulia Skripal/Facebook via AP)

LONDON - The international chemical weapons watchdog on Thursday confirmed Britain's finding that a former Russian spy and his daughter were poisoned with a nerve agent, as Russia continued to deny suggestions that it was behind the attack.

Investigators from the Organization for the Prohibition of Chemical Weapons said the nerve agent was "of high purity." Britain says that means only a state with a sophisticated laboratory could have manufactured it.

The watchdog's report does not say who was responsible for the attack, since that was outside the scope of its mission. The OPCW's job was to identify the poison, not to trace its origins or assign blame.

Britain blames Russia for the March 4 poisoning of Sergei Skripal and his daughter Yulia in the English city of Salisbury.

Russia denies involvement, and says Britain hasn't shared any evidence for its assertion.

Russian Foreign Ministry spokeswoman Maria Zakharova on Thursday accused Britain of waging a defamation campaign against Russia, manipulating public opinion and hiding facts. She said Moscow will continue to press Britain to share evidence in the case.

Britain has asked for a meeting of OPCW 's executive council on Wednesday to discuss the organization's findings, and Britain is also seeking a meeting of the U.N. Security Council next week on the chemical weapons report.

In a published summary, the OPCW did not name Novichok, the type of nerve agent previously cited by British Prime Minister Theresa May. But it confirmed "the findings of the United Kingdom relating to the identity of the toxic chemical that was used in Salisbury." It said the name and structure of the toxin were included in the full classified report, distributed to 192 member states of the organization.

The Novichok class of nerve agents was developed in the Soviet Union toward the end of the Cold War, and Britain says it has evidence Russia has continued to manufacture Novichok agents in the last decade. Russia denies this and says the nerve agent used on the Skripals could easily have been manufactured in another country.

The purity of the nerve agent makes it hard to tell when the agent was manufactured, since without impurities it does not degrade over time.

Britain says scientific analysis of the poison is only one of the factors that has led it to blame Russia.

Others include intelligence that Russia has made nerve agents and studied how to use them for assassinations, and the view of Russian President Vladimir Putin's government that traitors are legitimate targets.

But the U.K. does not possess a scientific smoking gun — a sample of Novichok from a Russian lab to compare with the Salisbury samples.

The poisoning has sparked a Cold War-style diplomatic crisis Russia and the West, including the expulsion of hundreds of diplomats from the two sides.

Georgy Kalamanov, Russia's deputy minister of industry and trade, told the Interfax news agency Thursday it's impossible to pinpoint the agent's origin and reaffirmed Moscow's demand for a probe that would involve Russia.

U.K. Foreign Secretary Boris Johnson welcomed the OPCW's report, saying tests in four independent laboratories around the world all returned the same results.

"There can be no doubt what was used and there remains no alternative explanation about who was responsible — only Russia has the means, motive and record," he said.

The findings come after Yulia Skripal rejected Russian Embassy assistance as she recovers at an undisclosed location. Yulia, 33, was released from the hospital earlier this week, but her 66-year-old father is recovering more slowly.

In a statement released by London's Metropolitan Police, Yulia Skripal said the embassy had offered assistance but "at the moment, I do not wish to avail myself of their services." She also said she did not yet want to speak to the media.

"Until that time, I want to stress that no one speaks for me, or for my father, but ourselves," she said.

The comment came after Yulia's cousin Viktoria gave a series of interviews about a telephone conversation between the two, leading the British government to claim that Russia was using Viktoria Skripal as a "pawn" in the poisoning dispute.

Russia's Embassy in London questioned the authenticity of Yulia's statement, saying it was crafted to support Britain's version of events and increases suspicions that she is being held against her will.

"The document only strengthens suspicions that we are dealing with a forcible isolation of the Russian citizen," the embassy said.

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Edith Lederer at the United Nations and Vladimir Isachenkov in Moscow contributed to this story.

News from © The Associated Press, 2018