MOSCOW - President Vladimir Putin vowed he would not allow Russia to slip into civil war after the leader of the Wagner mercenary force seized a key military headquarters overseeing the offensive in Ukraine.
The rapidly moving events mark the most serious challenge yet to the Kremlin chief's long rule and Russia's most serious security crisis since he came to power in late 1999.
Wagner chief Yevgeny Prighozin said his troops had taken control of the military command centre and an airbase in the southern city of Rostov-on-Don, and vowed to topple Moscow's top military leaders.
Responding in a televised nation address, Putin slammed his former ally -- whose private army provided some of the most successful shock troops in Moscow's offensive in Ukraine -- for a "stab in the back" that posed a threat to Russia's very survival.
READ: Putin says situation 'difficult' in Rostov in southern Russia
"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.
"This battle, when the fate of our people is being decided, requires the unification of all forces."
"What we have been faced with is exactly betrayal. Extravagant ambitions and personal interests led to treason," Putin said, referring to Prigozhin, who built a powerbase as a catering contractor to the Kremlin, and now runs a powerful private military force.
"All those who consciously stood on the path of betrayal, who prepared an armed rebellion, stood on the path of blackmail and terrorist methods, will suffer inevitable punishment, before the law and before our people," Putin vowed.
The Russian president's speech came shortly after Prighozin posted a message of his own, apparently filmed in Rostov-on-Don, accusing the Russian military leadership of betrayal and failure in the ongoing battle against Ukrainian forces.
"A huge amount of territory is lost. Soldiers have been killed, three, four times more than what it says in documents shown to the top," he said, accusing military commanders of hiding the true scale of Russian losses in Ukraine from the Kremlin.
"Military sites in Rostov, including an aerodrome, are under control," he said, adding that warplanes taking part in the Ukraine offensive "are leaving as normal".
"We are dying for the Russian people," he said, in an earlier audio message. "All of us are ready to die. All 25,000, and then another 25,000 ... We will destroy everything that stands in our way."
Russia's headquarters in Rostov-on-Don is a key logistical base for its offensive in Ukraine.