Wagner leader Yevgeny Prigozhin was photographed in St Petersburg during this week’s Africa-Russia summit.
He was seen shaking hands with Ambassador Freddy Mapouka, a senior official in the Central African Republic (CAR).
The image was posted on Facebook by Dmitri Syty, who reportedly manages Wagner’s operations in CAR.
It is the first confirmed sighting of Mr Prigozhin in Russia since Wagner’s failed mutiny in June.
Mr Prigozhin and Mr Mapouka’s meeting took place at the Trezzini Palace hotel in St Petersburg, BBC Verify confirmed.
BBC Verify used facial recognition software to compare known photographs of the CAR official with the picture featuring Prigozhin and got a 99% match, indicating the two images are of the same man.
Details of the interior seen in the background of the photo were also matched to the Trezzini Palace hotel which, according to Russian media, is owned by Prigozhin.
The lanyard worn by Mr Mapouka has a distinctive pattern, which is identical to that of the official lanyard worn by delegates at the summit.
Searches for the same image did not find any earlier copies, which indicates it has only appeared online recently.
There are several hundred Wagner mercenaries in diamond-rich CAR, helping the government fight rebel groups. The UK last week imposed sanctions on the two heads of Wagner’s operations in CAR, accusing them of torture and killing civilians.
The meeting follows Mr Prigozhin’s appearance in Belarus last week. A video on Telegram channels linked to the Wagner mercenary group shows him welcoming fighters and describing recent developments on the frontline in Ukraine as a “disgrace”.
He also hints that Wagner might rejoin the war at a later date.
During the Africa-Russia Summit, Russian President Vladimir Putin said he was ready to replace Ukrainian grain exports to Africa on both a commercial and aid basis to help avoid a “global food crisis”.
“We will be ready to provide Burkina Faso, Zimbabwe, Mali, Somalia, Central African Republic and Eritrea with 25-50,000 tonnes of free grain each in the next three to four months,” Putin said. These are all Russian allies, except Somalia which is suffering a severe humanitarian crisis.
Russia recently withdrew from a deal under which Ukrainian grain exports passed through the Black Sea to reach global markets, including Africa.
The EU said it believes Mr Putin is misleading African countries over his promise to send free grain to the continent. The European Commission said Russia was unlikely to honour its pledge.