The Russian capital and the regions of Rostov, which borders Ukraine, and Lipetsk announced on Saturday that they were stepping up their security arrangements after the head of Russian paramilitary group, Wagner, accused the Russian army of shelling his fighters.
On Friday, Yevgeny Prigozhin said he had ordered his men to march on the Russian defence ministry and appealed to government soldiers to join the uprising.
On Saturday, Russian President Vladimir Putin called Wagner's uprising a 'stab in the back', calling for unity.
The authorities in Moscow and the surrounding area say they have declared a counterterrorism state of emergency against the background of the armed uprising.
Wagner fighters are active in African countries such as Mali and Central African Republic, where they have helped the government of President Faustin-Archange Touadéra train the army and to maintain relative security in and around the capital Bangui.
Wagner fighters are also deployed in Mali, where the military government is battling an Islamist insurgency.
The men have been accused of committing atrocities.
Ukrainian President reacts
In his view, they reveal Russia's "obvious weakness", he posted on Twitter on Saturday. "Russia's weakness is obvious. Weakness on a massive scale. And the longer Russia keeps its troops and mercenaries on our (Ukrainian) territory, the more chaos, pain and problems it will have to deal with itself", said Volodymyr Zelensky.
Wagner on its way to Moscow?
According to Reuters, a convoy of Russian fighters from the Wagner group passed through the town of Voronezh, around 500 km from Moscow. At least one of the vehicles in the convoy was a truck carrying a battle tank. This advance suggests that the Russian group is getting closer to the capital.
Putin talks with allies
In a sign of growing concern in the Kremlin, Vladimir Putin held telephone conversations with his Belarusian and Kazakh counterparts, who are allies of Russia, to inform them of the current situation. The Kazakh President, Kassym-Jomart Tokayev, said during the talks that the current events were an internal Russian affair, stressing the importance of constitutional order and the rule of law in maintaining order in the country, according to a press release from the Kazakh Presidency.