Abramovich was taking part in informal peace negotiations in the Ukrainian capital, Kyiv, early in March when he began to feel ill, the source told the Guardian. Ukrainian MP Rustem Umerov was also part of the negotiation, and the men later left Ukraine for Poland, and then flew to Istanbul, where they received medical treatment.

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“It was during his first trip to Kyiv. Roman lost his sight for several hours. In Turkey, they were treated in a clinic, together with Rustem,” said the source.

The account backs up the claims of a potential poisoning first reported in the Wall Street Journal and by the investigative journalism outlet Bellingcat.

“Bellingcat can confirm that three members of the delegation attending the peace talks between Ukraine and Russia on the night of 3 to 4 March 2022 experienced symptoms consistent with poisoning with chemical weapons. One of victims was Russian entrepreneur Roman Abramovich,” wrote the outlet in a tweet.

Bellingcat said the symptoms included eye and skin inflammation, and piercing pain in the eyes.

“The three men experiencing the symptoms consumed only chocolate and water in the hours before the symptoms appeared. A fourth member of the team who also consumed these did not experience symptoms,” wrote Bellingcat, which said one of its investigators had been asked to provide an opinion on the incident by chemical weapons specialists.

“Based on remote and on-site examinations, the experts concluded that the symptoms are most likely the result of international poisoning with an undefined chemical weapon,” said Bellingcat,