The Wagner group cheif, Yevgeny Prigozhin, 62, released a series of messages from late Friday into Saturday, claiming that he and his mercenary troops had entered the southern Russian city of Rostov-on-Don and taken control of its military sites. 

Responding to the challenge in a televised address, Putin accused Prighozin, whose private army provided shock troops for Moscow's offensive in Ukraine, of a "stab in the back" that posed a threat to Russia's very survival.

"Any internal turmoil is a deadly threat to our statehood and to us as a nation. This is a blow to Russia and to our people," Putin said.

Prigozhin in return said Russian President Vladimir Putin was "deeply mistaken" in calling rebelling Wagner fighters "traitors" and ruled out surrender.

"On treason of the motherland: the president is deeply wrong. We are patriots of our motherland," Prigozhin, who launched a mutiny overnight, said in an audio message on Telegram. "Nobody plans to turn themselves in at the request of the president, the FSB (security service) or anyone else."

The rebellion comes at a time when Russia is “fighting the toughest battle for its future,” Putin said, as Western governments heap sanctions on Moscow and arm Ukraine.

Prigozhin's actions could have significant implications for the war. Orysia Lutsevych, the head of the Ukraine Forum at the Chatham House think tank in London, said infighting between the Defense Ministry and Wagner will create confusion and potential division among Russian forces.

“Russian troops in Ukraine may well now be operating in a vacuum, without clear military instructions, and doubts about whom to obey and follow,″ Lutsevych said. “This creates a unique and unprecedented military opportunity for the Ukrainian army.”

This revolt by the Wagner mercenary group consider the most serious challenge yet to the Kremlin chief's long rule, and Russia's most serious security crisis since the strongman Putin came to power in late 1999.

After Putin’s address, officials sought to reiterate their allegiance to the Kremlin and urged Prigozhin to back down.

Orthodox Church

The leader of Russia's Orthodox Patriarch Kirill on Saturday called for "unity" in the country and voiced support for President Vladimir Putin as Wagner mercenaries staged a rebellion.

"Today, when our brothers are fighting and dying on the frontlines... any attempt to sow discord within the country is the greatest possible crime that has no justification," Patriarch Kirill said in a statement.

Adding, "I support the efforts of the head of the Russian state, aimed at not allowing turmoil in our country."

Russian Parliament 

Speakers of both of Russia's houses of parliament said they backed Russian President Putin in his call to the Wagner mercenary group to halt a bid to oust the country's military leadership.

The head of the upper house of parliament Valentina Matvienko said Putin has members' "full support," while the speaker of the lower house Vyacheslav Volodin urged Russians to "support" the long-time leader.

Foreign Ministry 

Spokeswoman Maria Zakharova echoed Volodin’s sentiment, saying in a Telegram post that “we have one commander in chief. Not two, not three. One.″

Officials In Moscow-Occupied Ukraine 

The Russian-installed heads of Ukrainian regions occupied by Moscow expressed support for President Vladimir Putin who faces an extraordinary mutiny from the Wagner group.

"The Kherson region and the people of Kherson completely support our president!", the Russian-installed head of Ukraine's southern Kherson region said on Telegram.

The Kremlin-appointed head of the part of the Zaporizhzhia region controlled by Moscow, Yevgeny Balitsky, said the territory was "with the president."

Officials

Dmitry Medvedev, the former Russian president and the deputy secretary of the country's Security Council, has called for Russians to unite around Putin to "save" the country.

"Division and betrayal is the path to the greatest tragedy, a universal catastrophe," Medvedev, who has been of Putin's most trusted allies for years and an ardent war supporter, wrote on Telegram.

"We won’t allow it," he added.

Ramzan Kadyrov, the strongman leader of the Chechnya region who used to side with Prigozhin in his criticism of the military, also expressed his full support of Putin's “every word.”

“We have the commander in chief, elected by the people, who knows the situation to the slightest detail better than any strategist and businessman,” Kadyrov said. “The mutiny needs to be suppressed.”

Kadyrov, also announced Saturday that he had sent Chechen units to "zones of tension" in Russia, after Wagner mercenaries launched a mutiny in the country.

"Defence ministry and National Guard fighters of the Chechen Republic have already left for the zones of tension," Kadyrov said on Telegram. "The rebellion must be put down, and if harsh measures are necessary, we are ready!"

Turkish leader Recep Tayyip Erdogan voiced full support for Russian President Vladimir Putin in a phonecall to discuss the Wagner mercenary group's armed insurrection in Russia.

"The president of Russia gave information about the situation in the country in connection with an attempted armed rebellion. The president of the republic of Turkey expressed full support for the steps taken by the Russian leadership," the Kremlin said in a statement.