Russian oligarch Roman Abramovich arranged to have a private meeting with President Vladimir Putin and has made a strong case to end the war with Ukraine, reports said.
Turkey said Abramovich, who is sanctioned by European nations over Russia's invasion of Ukraine, was part of the Russian delegation at peace talks in Istanbul this week and is "sincerely" working to end the war.
Abramovich made a surprise appearance at Tuesday's talks in Istanbul however video footage showed him sat among observers rather than with the two negotiating teams.
Speaking to reporters on a flight from Uzkebistakn, Turkish President Tayyip Erdogan said Abramovich's presence showed Russian President Vladimir Putin "believes, trusts him", according to broadcaster NTV and others.
"Abramovich participated in the negotiations as part of the Russian delegation. Rather than looking at who was at the table, we should look at on whose behalf they were there," he said.
Turkish Foreign Minister Mevlut Cavusoglu told broadcaster A Haber that Abramovich has been liaising between Kyiv and Moscow since the February 24 invasion and working "sincerely" to end the fighting.
"Of course, official talks are important, negotiations are important, but public opinion is sensitive, everyone wants to maintain their position, and there are channels that should be kept open between leaders and countries.
"Here, Abramovich plays a useful role," he said.
Kremlin spokesman Dmitry Peskov had said Abramovich was not an official member of the Russian delegation, but acknowledged his presence to "enable certain contacts".
Reports said Abramovich even went to Kyiv on at least two occasions to meet President Volodymyr Zelensky
But Abramovich’s critics claim he is using the talks to try and salvage his overseas assets.
"I’m not sure how much his involvement in this mediation is real and effective, and how much of it is a PR tool," Vladimir Ashurkov, executive director of the Anti-Corruption Foundation founded by the jailed Russian dissident Alexei Navalny told the Financial Times.
"He’s a creative guy, and he has creative people working for him, so it can just be a way to have a chance to ease the sanctions."
A member of the military alliance NATO, Turkey shares a maritime border with Ukraine and Russia in the Black Sea, has good ties with both and has offered to mediate.
It has supported Kyiv, but also opposes sanctions on Moscow, including measures against Abramovich and other Russian billionaires.
Abramovich had sought to sell his English soccer club Chelsea, a process taken out of his hands by the British government when it blacklisted him.
Superyachts linked to him, together worth an estimated $1.2 billion, have been docked at Bodrum and Marmaris in southwest Turkey since last week.
Sources have said he and other wealthy Russians were looking to invest in Turkey given sanctions elsewhere.
