By Pavel Polityuk
KYIV (Reuters) -Russia said on Monday it was battling a cross-border incursion by saboteurs who burst through the frontier from Ukraine, in what appeared to be one of the biggest attacks of its kind since the war began 15 months ago.
The governor of Russia's Belgorod region, Vyacheslav Gladkov, said a Ukrainian "sabotage group" had entered Russian territory in the Graivoron district bordering Ukraine and was being repelled.
But the Ukrainian outlet Hromadske cited Ukrainian military intelligence as saying two armed Russian opposition groups, the Liberty of Russia Legion and the Russian Volunteer Corps, both consisting of Russian citizens, were responsible for the attack.
A Ukrainian presidential adviser said on Twitter that the Kyiv government was watching the situation with interest but "has nothing to do with it".
The Russia Volunteer Corps published video footage late on Monday which showed what it said was a fighter inspecting a captured armoured vehicle. Another video showed what it said were fighters operating an armoured vehicle on a country road.
Other videos posted on Russian and Ukrainian social media channels showed pictures and video of what were described as captured Russian servicemen and their identity documents.
Reuters was not able to independently verify the situation.
GOVERNOR IMPOSES 'COUNTER-TERRORIST' MEASURES
Kremlin spokesman Dmitry Peskov said Russian President Vladimir Putin had been informed and that work was under way to drive out the "saboteurs", the state-run RIA Novosti news agency reported.
Belgorod governor Gladkov said on Telegram that at least eight people had been wounded and three houses and an administrative building damaged. In a later briefing streamed on social media, Gladkov said a large part of the local population had left and that he had imposed a "counter-terrorist operation" that restricts movement and communications.
The Telegram channel Baza, which has links to Russia's security services, said there were indications of fighting in three settlements along the main road leading into Russia. The "Open Belgorod" Telegram channel said power and water had been cut off to several villages.
The Liberty of Russia Legion said on Twitter it had "completely liberated" the border town of Kozinka. It said forward units had reached the district centre of Graivoron, further east.
"Moving on. Russia will be free!" it wrote.
Ukrainian social media users made regular reference to what they called the "Belgorod People's Republic" - a nod to events in eastern Ukraine in 2014 when Russia-backed militias purporting to be rebels against the Kyiv government declared "people’s republics" in the eastern Ukrainian provinces of Donetsk and Luhansk. Russia launched a full-scale invasion of Ukraine in February last year.
BAKHMUT BATTLE RAGES ON
The Kremlin said the incursion aimed to distract attention from the eastern Ukrainian city of Bakhmut, which Russian forces claim to have captured in its entirety after more than nine months of fighting.
Moscow says capturing Bakhmut opens the way to further advances in the eastern industrial region known as the Donbas bordering Russia. Ukraine says its advance on the Russian forces' flanks is more meaningful than its withdrawal inside Bakhmut itself, and Russia will have to weaken its lines elsewhere to send reinforcements to hold the shattered city.
There were 25 clashes on the main sectors of the frontline with the epicentre of fighting remaining Bakhmut and Maryinka further south, the General Staff of the Ukrainian Armed Forces said in a statement on Monday night.
Russian forces continued offensive actions including air strikes on Bakhmut and on the village of Ivanivske on its western fringe, the statement said. At least 12 towns and villages in the area came under shell fire, including Bakhmut and Ivanivske, it said.
Separately on Bakhmut, Serhiy Cherevatyi, spokesperson for the eastern group of Ukrainian forces, told Ukrainian television: "In the past 24 hours, Ukrainian troops have made steady progress, advancing 250-400 metres on the flanks and establishing a foothold. Even though these advances are gradual, it is better when such advances are well planned."
Reuters could not independently verify the reports.
Meanwhile, the United Nations expressed concern on Monday that Ukraine's Black Sea port of Pivdennyi (Yuzhny) has not received any ships since May 2 under a deal allowing the safe wartime export of grain and fertilizer.
(Reporting by Pavel Polityuk, Kevin Liffey and Reuters bureaux; writing by Peter Graff and Nick Macfie; editing by Frank Jack Daniel, Mark Heinrich, Grant McCool and Cynthia Osterman)