Roman Abramovich suffered symptoms of chemical weapons poisoning after taking part in peace talks in Ukraine earlier this month.
The Wall Street Journal report that the Chelsea owner was one of three members of the delegation that complained of searing eye pain and peeling of their skin on their face and hands. The other two victims were from the Ukrainian side of the delegations.
One of the others to report symptoms were Ukrainian politician, Rustem Umerov.
All three have recovered, according to the reports, and their lives are not in danger. A source close to Abramovich said it wasn't clear who had targeted the group.
Abramovich is subject to UK sanctions due to his ties to Russian president, Vladimir Putin. As a result, the 55-year old is trying to sell Chelsea via the Raine Group merchant bank.
He'd positioned himself as a potential peacemaker shortly after Russia's invasion of Ukraine on February 24. Last week, The Kremlin confirmed Abramovich had been involved in early talks between the two countries, but that proceedings were now solely the domain of official channels.
— Noga Tarnopolsky (@NTarnopolsky) March 14, 2022
Those talks reportedly took place on March 3 in Ukraine, before the Abramovich party returned to a Kyiv hotel where they felt initial symptoms.
The following day they made their way from Kyiv to Lviv in the west of Ukraine, before crossing the border to Poland and flying to Istanbul.
A Bellingcat report says the Abramovich trio consumed only chocolate and water in the hours preceding their first symptoms.
They claim the symptoms were the result of "international poisoning with an undefined chemical weapon."
While the source of the chemical weapon has not been identified, Russia does have form in this area.
In 2006, former KGB agent turned dissident Alexander Litvinenko died following radiation poisoning, for which the European Court of Human Rights ruled last year that Russia were responsible.
Last year, a third Russian military intelligence officer was charged with the attempted assassination of former Russian spy Sergei Skripal and his daughter Yulia with a novichok nerve agent in March 2018.