VLADIMIR Putin blasted the Wagner mercenary army who have vowed to storm Moscow as "criminals" and their actions as "treason".
The Wagner group, led to by warlord Yevgeny Prigozhin, have seized military facilities in two cities and announced an "armed rebellion" against Russia's military.
Putin is today facing one of the biggest challenges to his iron-fist rule since he took power in the Kremlin more than two decades ago.
He has furiously declared Wagner's "internal mutiny" as a "mortal blow" to Russia - "a knife in the back of our people".
Wagner boss Prigozhin - known as Putin's "chef" - vowed to "punish" Russia after he blamed the Kremlin for a missile attack on a Wagner training camp in Bakhmut, Ukraine, which killed dozens.
Early on Saturday, he stormed a Russian army HQ in Rostov-on-Don and seized control of military facilities in Voronezh - as he vowed to march toward the Russian capital.
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In a televised speech this morning, Putin responded directly to the challenge: "This is a criminal campaign. It is equivalent to armed mutiny. Russia will defend itself and repel this move.
"We are fighting for the life and security of our citizens and our territorial integrity. Everything has to be done in order to put this danger to rest.
"It is an attempt to subvert us from inside. This is treason. In the face of those who are fighting on the front, this is a stab in the back of the troops and the people of Russia."
The Russian president also warned of "inevitable punishment" for those attacking "the motherland", vowing to defend Russia against "anarchy".
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Extraordinary pictures show the Russian military building in Rostov surrounded by tanks and troops from the Wagner Group.
Fierce battles are said to be raging in Voronezh as dramatic footage appeared to show a Russian Antonov An-26 being shot down by Wagner forces.
Elsewhere in the city, an oil depot was blown up - with video showing a helicopter flying overhead just seconds after a massive explosion.
Prigozhin and his troops have been fighting in Putin's shambolic war in Ukraine - but the Wagner boss has become a vocal critic of Russia's military leadership.
In his fuming tirade today, he promised Wagner would topple Moscow's military leadership and claimed his 25,000 fighters were "ready to die".
He said: "We will destroy anyone who stands in our way... we are moving forward and will go until the end."
Prigozhin called for an armed rebellion aimed at ousting Russia's top generals and defence minister Sergei Shoigu.
Russia's security services responded to his declaration of an armed rebellion by calling for his arrest - and security was immediately ramped up in both Rostov and Moscow.
Footage from Moscow showed armoured vehicles racing along the streets - as US officials are "closely watching" events unfold.
Roadblocks manned by special forces were set up around the city as military officials launch a desperate bid to secure both the Kremlin and the Duma building, Russia’s parliament.
Russia’s army chief General Valery Gerasimov reportedly fled shortly before Wagner surrounded Russia’s war command HQ in Rostov-on-Don.
Prigozhin demanded Shoigu and army chief Gerasimov appear before him - or he would go to Moscow, with his forces already on the road.
He was seen flanked by Putin's humiliated deputy defence minister Yunus-Bek Yevkurov as he made the demand.
"Until they're gone, we're here, we're blockading the city of Rostov and we're going to Moscow," Prigozhin warned.
Prigozhin claimed regular Russian troops are switching to his side in the coup bid.
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The UK Ministry of Defence described the rebellion as "the most significant challenge to the Russian state in recent times".
"Over the coming hours, the loyalty of Russia’s security forces, and especially the Russian National Guard, will be key to how the crisis plays out," it warned.