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Wagner chief Yevgeny Prigozhin said Saturday his units were hit by a helicopter on a highway and threatened to “destroy everything” in his way, in an audio message posted on his Telegram channel.
It's unclear exactly where the units were.
"One of the assault squads came under fire from the helicopters. The Wagner units are intact, the helicopter is destroyed and is burning in the forest,” Prigozhin said, adding “we will take it as a threat and destroy everything around us.”
CNN is unable to verify these claims and any video evidence of this.
Prigozhin also said his units are “ready to die.”
“Because we are dying for the Russian people, that must be liberated from those people who are striking at the civilian population, which they just hit in Rostov from helicopters,” he said.
This comes as Moscow Mayor Sergei Sobyanin said Saturday in a Telegram post that “in connection with the incoming information, antiterrorist measures are being taken in Moscow aimed at strengthening security measures.”
“Additional control on the roads has been introduced. Limitations on holding the public events are possible,” Sobyanin added.
Moscow Mayor Sergei Sobyanin says that "anti-terrorist measures" are being carried out in the city as a result of "incoming information," according to an update on his Telegram group.
"In connection with the incoming information, antiterrorist measures are being taken in Moscow aimed at strengthening security measures," Sobyanin said.
The measures include "additional control on the roads" and "limitations on holding public events."
At least two people were killed and eight others injured when debris hit a tall building in Kyiv's central Solomyanskyi district, a Ukrainian military official said.
Serhiy Popko, head of the Kyiv region military administration, said the debris hit a 24-story building. Previously, the Kyiv mayor reported it was 16 stories.
"Clarification of information regarding the consequences of debris hitting a 24-story building in the Solomyanskyi district. At the moment, two dead have been identified. Injured — eight people. Two were hospitalized, the rest received medical assistance on the spot. About 40 cars parked in the parking lot were damaged," Popko said on Telegram Saturday.
The Kyiv city military administration says air defense systems destroyed more than 20 missiles in airspace around Kyiv overnight.
Videos posted to social media purport to show military helicopters flying over the Russian city of Rostov and a number of armored vehicles on city streets on Saturday morning.
The videos have been geolocated by CNN to Teatral'nyy Prospekt, in Rostov.
It is currently unclear whose command these vehicles are under the control of. Rostov region Governor Vasily Golubev asked residents on Saturday morning to stay calm and not leave their homes.
Rostov is in Russia's south, near to the border with southeastern Ukraine, and about 1,000 kilometers (620 miles) from Moscow.
Tensions between Yevgeny Prigozhin and the Russian defense ministry are finally coming to a head, with the Wagner leader threatening to attack Russian troops in retaliation for what he says was a deadly strike against his own paramilitary forces.
In extraordinary developments, the Russian security services accused Prigozhin of launching a coup attempt and have launched a criminal prosecution which could eventually see him jailed in what would be a dramatic fall from grace for one of Russia’s most prominent and outspoken figures.
For months, Prigozhin has been lambasting Russia’s High Command for mishandling the Ukraine war, repeatedly accusing the defense minister and the country’s military chief of incompetence.
Earlier this month, the Kremlin demanded all Russian mercenaries sign contracts with the Russian defense ministry, in a move seen as an attempt to control Wagner.
But Prigozhin remained defiant, refusing to comply and voicing increasingly vitriolic tirades against the Russian military hierarchy.
In the hours before the alleged attack on the Wagner camp, Prigozhin posted more inflammatory comments on social media, accusing the defense ministry of deceiving Russian President Vladimir Putin about the threat posed by Ukraine ahead of his February 2022 invasion. He also questioned Russian motives for the war.
Now, Moscow has been placed on alert in a response to Prigozhin’s call for a "march for justice" against defense officials he says are responsible for attacking Wagner, while his mercenary forces are said to be entering the southern Russian region of Rostov.
CNN cannot independently verify the claims.
Meanwhile, next door in Ukraine, defense officials say they are watching closely as Russia seems to plunge into turmoil.
A Russian state media correspondent said the situation is calm in the southern city of Rostov on Don and a street closure is only partial.
The eye-witness account comes after Wagner chief Yevgeny Prigozhin said his fighters were entering the Russian Rostov region, which neighbors Ukraine. Prigozhin earlier threatened to retaliate against Russia's military after accusing the leadership of killing his men in a strike on a camp.
According to the RIA Novosti correspondent, traffic is blocked on one side of Budennovsky Avenue, as well as on part of Pushkinskaya Street.
In that area, there is one armored personnel carrier, one Patrol-A armored car, one Tigr-M armored off-road vehicle, and several fighters with machine guns, the reporter said.
Traffic is generally normal, and a few people are on the streets.
Rostov region Governor Vasily Golubev is asking residents to stay calm and to not leave their homes.
"Dear fellow countrymen! The current situation requires a maximum concentration of all efforts to maintain order. Law enforcement agencies are doing everything necessary to ensure the safety of the region's residents. I ask everyone to stay calm and do not leave your homes unless it is necessary," Golubev said in a Telegram post Saturday.
The warnings come after Wagner chief Yevgeny Prigozhin said his fighters were entering the Russian Rostov region, which neighbors Ukraine. Prigozhin earlier vowed retaliation after accusing Russia's defense ministry of killing a "huge amount" of his mercenaries in a strike on a camp.
A local journalist said the streets appear calm in Moscow, but that there is heightened security at government agencies.
Russian journalist Vasily Polonsky told CNN people in Moscow do not appear to be afraid at all, but he heard people talking about Wagner chief Yevgeny Prigozhin as they walk down the streets. On Friday night, he saw people out playing music, drinking and partying. He didn't see authorities asking people to leave the streets.
But Polonsky said military equipment is visible in central Moscow and there is some equipment behind the main building of the Ministry of Interior. He said he walked to most buildings of the government agencies and spotted at least one or two police cars next to each one. The most guarded building appeared to be the Ministry of the Interior.