Mercenary chief Yevgeny Prigozhin said on Saturday he had taken control of the Russian city of Rostov-on-Don as part of an attempt to oust the military leadership, in what the authorities said was an armed mutiny.
Following are some facts about the businessman and founder of the Wagner Group.
* With aggressive PR, foul language and a frequent presence near the front lines, the shaven-headed Prigozhin is one of the most visible faces of the war, having recruited thousands of Russian prisoners to fight for Wagner and feuded openly with the defence ministry over military plans and ammunition supplies.
* Prigozhin, 62, has for decades been known as "Putin's chef" due to his company's Kremlin catering contracts. It's unclear how friendly he and Russian President Vladimir Putin are, but they know each other and both men were born and raised in St Petersburg.
* After serving a long prison sentence in the 1980s, Prigozhin started out selling hotdogs in his hometown. He soon began to build up a stake in a chain of supermarkets, and eventually opened his own restaurant and catering company.
* His restaurant gained a reputation for its fine food and was soon hosting city dignitaries including then deputy mayor Vladimir Putin.
* From there, Prigozhin's catering firm Concord began to win government supply contracts, taking its operations to a much bigger level.
* Prigozhin admitted last September that he had founded the private military group in 2014, the year Russia annexed Crimea from Ukraine. It was his first public confirmation of a link he had previously denied and sued journalists for reporting. The Wagner Group has fought in Libya, Syria, the Central African Republic and Mali, among other countries.
* The group also provided support to Russia-backed separatists who seized a chunk of Ukraine's eastern Donbas region in 2014.
* Last month the group seized the eastern Ukrainian city of Bakhmut after some of the war's most brutal fighting. During the onslaught, however, Prigozhin broke the taboos of Putin's tightly controlled political system with foul-mouthed insults of Moscow's top brass.
* Afterwards, he issued a video thanking the Kremlin, even as he launched into his favourite rant: The alleged treachery of Putin's top brass, in particular Defence Minister Sergei Shoigu and Chief of the General Staff Valery Gerasimov.
* In Prigozhin's most memorable video, on May 5, he showed a field of dead Wagner mercenaries who he said had perished due to a lack of munitions caused by Shoigu and Gerasimov.
* The United States and European Union have imposed sanctions on Prigozhin for his role in Wagner. They also accuse him of funding a troll farm known as the Internet Research Agency that Washington says tried to influence U.S. elections.