The local government in Voronezh region urged residents to avoid the M-4 north-south motorway connecting Moscow because a military convoy was on the move.

Hours after the chief of the mercenary group Wagner vowed to oust Russia’s military leadership, videos on social media purportedly showed its forces skirting Rostov-on-Don, home to the Russian military headquarters for the southern region and also oversees the fighting in Ukraine. There were also reports of clashes between members of the mercenary group and the Russian troops in the Pavlovsk district of the Voronezh Region.

Wagner chief Yevgeny Prigozhin’s call for an armed rebellion aimed at ousting Russia’s defence minister Sergei Shoigu is seen as his most direct challenge to President Vladimir Putin. Meanwhile, security has been beefed up in Moscow, indicating the serious nature of the threat.

Prigozhin claimed early Saturday that his forces had crossed into Russia from Ukraine and had reached Rostov, saying they faced no resistance from young conscripts at checkpoints and that his forces “aren’t fighting against children.”

“But we will destroy anyone who stands in our way,” he said in one of a series of angry video and audio recordings posted on social media beginning late Friday. “We are moving forward and will go until the end.”

In a new audio message, Prigozhin said that his 25,000-strong force was “ready to die” as he vowed to topple Russia’s military leadership.

“All of us are ready to die. All 25,000, and then another 25,000,” Yevgeny Prigozhin said in a new audio message. “We are dying for the Russian people.”

Anti-Kremlin figure Mikhail Khodorkovsky has, meanwhile, urged Russians to support Wagner.

“We need to help now, and then, if necessary, we will fight this one, too,” Khodorkovsky, a former oil tycoon who fell foul of the Kremlin, wrote on social media. He said it was important to back “even the devil” if he decided to take on the Kremlin. “And yes, this is just the beginning.”

The Wagner forces have played a crucial role in Russia’s war in Ukraine, succeeding in taking Bakhmut where the bloodiest and longest battles have taken place, Bakhmut. On Friday, Prigozhin, who has increasingly criticized Russia’s military leadership, claimed that the chief of the General Staff, Gen. Valery Gerasimov, scrambled warplanes to strike his convoys, which were driving alongside vehicles with civilians inside them.

Prigozhin also claimed that his mercenaries shot down a Russian military helicopter that fired on a civilian convoy.