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

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.

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.

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

The situation in Belgorod marks “the first time” that Ukrainian-backed 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.

Regional governor Vyacheslav Gladkov said that at least three people had been injured in the attacks: “They are in the hospital in a state of moderate severity. All necessary medical assistance is provided”.