According to Russian authorities, a gang of saboteurs entered from Ukraine into Russia’s Belgorod region, resulting in fights that injured numerous persons.
Vyacheslav Gladkov, the local governor, said Russian forces were looking for the group, which he alleged had attacked the Grayvoronsky region near the border.
The Russian president had been informed, according to Vladimir Putin’s spokeswoman.
Ukraine denies culpability, claiming that the attack was carried out by Russian residents from two paramilitary groups.
Six people were injured, according to Mr Gladkov, including two people admitted to hospital after the village of Glotovo was bombarded and three people who suffered shrapnel wounds in the town of Grayvoron.
According to him, fighting had also damaged three residences and a local administrative office.
The governor later announced the commencement of a “counter-terrorist operation” in the region, granting officials special powers such as identity checks and communications surveillance.
BBC Verify has been checking footage from the Belgorod region that surfaced on social media earlier today.
So far, the team has discovered a video that appears to have been shot from a drone and shows six armored vehicles near a border checkpoint south of Belgorod. In addition, BBC Verify has geolocated footage of helicopters in the area.
The material is current, although it is difficult to determine the exact chronology of events from the videos.
According to Kyiv, individuals behind the continuing disturbance are members of the Liberty of Russia Legion and the Russian Volunteer Corps (RVC).
The Liberty of Russia Legion, a Russian militia based in Ukraine that claims to be working within Russia to oust President Putin, announced on Twitter on Monday that it has “completely liberated” the border town of Kozinka. It stated that forward forces had arrived in Grayvoron, further east.
However, Mr Putin’s spokesman, Dmitry Peskov, told Russian news agencies that efforts were underway to eliminate the sabotage group, and that its purpose was to divert attention away from Bakhmut, an eastern Ukrainian town that a Russian mercenary group claims to have taken control of after months of intense and bloody fighting.
“We completely understand the purpose of such sabotage – to divert attention away from Bakhmut, to minimize the political impact of the Ukrainian side’s loss of Artemovsk [Bakhmut],” he said.
According to Kyiv, it still controls portions of the city.
Ukraine’s presidential advisor, Mikhaylo Podolyak, said his country was observing events in Belgorod “with interest,” but that his country “has nothing to do with it.”
“As you know, tanks can be purchased in any Russian military store, and underground guerrilla groups are made up of Russian citizens,” he continued.
Previously, Ukraine denied responsibility for alleged sabotage strikes on Russian territory.