CNN  — 

A group of anti-Putin Russian nationals – who are aligned with the Ukrainian army – has claimed responsibility for an attack in Russian’s southwestern region of Belgorod, as Moscow said it was fighting a group of saboteurs there.

Shelling damaged an administrative building, several residential buildings, and a kindergarten in the area, according to regional governor Vyacheslav Gladkov, who said there were no fatalities.

In a Telegram post, groups calling themselves the “Freedom of Russia Legion” and “Russian Volunteer Corps” said they had “liberated” a settlement in the Belgorod region, which borders Ukraine.

A Ukrainian official acknowledged that the units had carried out an operation in the area but insisted they were acting independently.

“We can confirm that this operation was carried out by Russian citizens,” Andriy Yusov, a representative of Ukraine’s defense intelligence agency, told CNN.

He said the units were “part of defense and security forces” when they were in Ukraine, but were independent from Kyiv when they were not: “In Russia they are acting as independent entities.”

Kremlin spokesperson Dmitry Peskov said the Kremlin’s forces were working to push out a “sabotage and reconnaissance group,” according to state media TASS.

The situation in Belgorod marks “the first time” that Ukrainian-aligned forces have launched “a cross-border land operation against Russian targets,” according to CNN’s Sam Kiley.

“This is on a significant scale, and clearly intended to cause considerable consternation among the local authorities at the very least, if not at the level of the Kremlin,” Kiley told CNN’s Lynda Kinkade on Connect the World.

A helicopter circles over Russia's Belgorod region, the site of fighting between Russian defectors and pro-Kremlin troops amid the war in Ukraine.

‘The situation remains extremely tense’

At least eight people had been injured in the attacks, but there were no deaths among civilians in Belgorod, according to Gladkov, the regional governor.

“The situation remains extremely tense. A sabotage and reconnaissance group, the Ministry of Defense and all law enforcement agencies have entered the territory to carry out combat missions to protect our country,” Gladkov said in a live-streamed address on Monday.

Gladkov said that the Belgorod government is “completing a house tour of the border villages” and in the town of Graivoron to ensure the safety of the local population.

He added that “most of the population left the territory” with personal transportation and the local government is providing assistance for those who do not have the opportunity to leave on their own.

He also noted that the head of the district Gennady Ivanovich Bondarev, is working with the Ministry of Emergency Situations and the police to evacuate people.

He said earlier that Russian troops, the border service, the National Guard and the FSB “are taking the necessary measures to eliminate the enemy.”

Air defenses struck down an unmanned aerial vehicle (UAV) in the region, Gladkov said, adding that there were no victims and Russian authorities are looking into any potential damage on the ground.

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Aleksey Baranovsky, a representative of the Kyiv-based Russian Armed Opposition Political Centre – the political wing of the Freedom of Russia Legion – told CNN that the operation had started Sunday night and fighting was “ongoing.”

He would not specify the number of fighters who had crossed the border into Russia.

Baranovsky said the group wanted to “liberate our motherland from the tyranny of Putin.”

In a Telegram post, the groups said they had “fully liberated the settlement of Kozinka of Belgorod region. [The] first groups have entered Grayvoron.”

In a separate incident Monday evening, the Freedom of Russia Legion posted a video on Telegram that appears to show the blue and white so-called flag of free Russia flying over Moscow State University.

Other videos posted by the group also appear to show another Russian opposition flag flying over various areas of the Russian capital.

The group did not claim direct responsibility for the incidents and CNN could not independently verify the reports.

What is the Freedom of Russia Legion?

The Freedom of Russia Legion numbers a few hundred of diehard, battle-hardened Russian volunteers fighting their own people as part of the Ukrainian armed forces.

Caesar is a member of the group. He is a former teacher, a father and has a wife living in Kyiv. He told CNN last year that he had dedicated his life to toppling Russian President Vladimir Putin and marching into Red Square and the Kremlin itself.

He is a devoted member of the Orthodox Church and is nostalgic for the Tsarist era that predated the Soviet Union. His unit is well-equipped with modern armored vehicles, gunsights and the latest automatic weapons.

The Legionnaires themselves have admitted that they’re often treated with suspicion by Ukrainian soldiers but hope to win them over with gallantry on the battlefield.

Their apparent incursion along a border that is frequently used by Russian mortar teams and artillery as a firebase for attacks inside Ukraine will help further cement their reputation.

It also serves as part of ongoing psychological operations intended to undermine support for the war in Russia and the fighting spirit of Russian soldiers themselves – signaling that they could be attacked at any time and even by their own countrymen.

Peskov, the Kremlin’s spokesperson, said: “Russian forces are working to push out the Ukrainian sabotage and reconnaissance group from the territory of the Russian Federation and destroy it. There are enough forces and means,” he told reporters.

He made reference to Bakhmut, which has garnered an outsized importance in the conflict as Russian forces battle to capture the eastern Ukrainian city while failing to make gains elsewhere.

CNN’s Uliana Pavlova contributed reporting.