Chelsea owner Roman Abramovich was pictured at talks in Turkey on Tuesday as he and others attempted to broker peace between Russia and Ukraine.
Russian Abramovich has been sanctioned by both the European Union and the UK government for alleged links to Russian president Vladimir Putin.
But the 55-year-old is currently acting as an unofficial mediator in negotiations hosted by Turkish president Recep Tayyip Erdogan.
Earlier this week it was reported by the Wall Street Journal that Abramovich had been the victim of an attempted poisoning during previous talks.
Abramovich has also been present at meetings in Kyiv, Moscow and Belarus since Russia invaded Ukraine.
According to the Wall Street Journal, Abramovich and Ukrainian peace negotiators at a previous meeting in Kyiv on March 3 suffered symptoms including red eyes, constant and painful tearing, and peeling skin on their faces and hands.
It was suggested by some that the alleged poisoning attempt was down to Russian agents whose aim had been to disrupt the peace talks. Others claimed it could have been intended as a warning for Abramovich not to betray Russia.
But Russia has denied claims it targeted Abramovich and fellow delegates with poison.
“This is part of information sabotage, part of an information war,” Kremlin spokesman Dmitry Peskov told journalists, as reported by First Post.
“It goes without saying that these reports do not correspond to reality.”
But Ukrainian foreign minister Dmytro Kuleba has advised Abramovich and fellow negotiators to take precautions.
“I advise anyone going for negotiations with Russia not to eat or drink anything, preferably avoid touching surfaces,” said Kuleba in an interview with Ukrayina 24, which was translated by Sky News