President Vladimir Putin said on Thursday Russia was fighting off a "terrorist attack" in the southern Bryansk region bordering Ukraine, and vowed to crush what he said was a Ukrainian sabotage group that had fired at civilians.
Ukraine accused Russia of staging a false "provocation", but also appeared to imply some form of attack had indeed been carried out by Russian anti-government partisans.
Amid reports of shelling and sporadic sabotage, Russia's border regions have become increasingly volatile since Moscow invaded Ukraine a year ago in what it called a "special military operation".
Putin, in a televised address, accused the group of opening fire on civilians, including children. Bryansk Governor Alexander Bogomaz had earlier said that the Ukrainians had shot and killed one person and injured a child.
"They won't achieve anything. We will crush them," said Putin, saying the group was made up of the kind of people who wanted to rob Russia of its history and language.
In two videos circulating online, armed men calling themselves the "Russian Volunteer Corps" said they had crossed the border to fight what they called "the bloody Putinite and Kremlin regime."
Calling themselves Russian "liberators", the armed men called on Russians to take up arms and rise up against the authorities. They said they did not open fire on civilians.
Reuters could not immediately verify the videos' authenticity.
Kremlin spokesman Dmitry Peskov told reporters that law enforcement agencies would determine who was responsible and Putin was being briefed by security chiefs on the situation.
KIEV ACCUSES MOSCOW OF 'PROVOCATION'
Ukrainian presidential adviser Mykhailo Podolyak wrote on Twitter: "The story about (a) Ukrainian sabotage group in RF (Russian Federation) is a classic deliberate provocation."
He said Russia "wants to scare its people to justify the attack on another country & the growing poverty after the year of war."
A spokesman for Ukrainian military intelligence suggested the makeup of the sabotage group was a sign of internal strife inside Russia.
"These are people who with weapons in their hands are fighting the Putin regime and those who support it... Maybe Russians will begin to wake up, realise something and take some concrete steps," Andriy Yusov told Ukrainian outlet Hromadske.
Russia's FSB security service said in a statement to Russian news agencies on Thursday that its own forces and the army were trying to liquidate what it described as "an armed group of Ukrainian nationalists" who had crossed the border.
Bryansk Governor Bogomaz said on his Telegram channel: "Today, a Ukrainian sabotage and reconnaissance group penetrated the Klimovsky district in the village of Lubechanye. "Saboteurs fired on a moving car. As a result of the attack, one resident was killed and a ten-year-old child was wounded."
He said Ukrainian armed forces had carried out a drone attack and fired artillery at other areas near the border.
Reuters was unable to immediately verify the reports.
British military intelligence said on Wednesday that Russia was launching drone attacks on Ukraine from the Bryansk region, which lies to the north of Ukraine and is closer to its capital Kyiv than other launch sites.
The Russian state news agency TASS said the Ukrainians had infiltrated two villages, taking local residents hostage in one of them. The RIA news agency said several people had been taken hostage in a store in the village of Lubechanye, less than one kilometre from the border with Ukraine.
Russia has accused Ukrainian saboteurs of infiltrating Bryansk before.
In December, the FSB said a four-person Ukrainian "sabotage group" had been "liquidated" while trying to enter Bryansk.
Putin told the FSB this week that it needed to step up its guard against espionage and what he called terrorist threats emanating from Ukraine and the West.
"Your task is to put a barrier in the way of sabotage groups, to stop attempts to illegally transport weapons and ammunition into Russia," he said in a speech on Tuesday.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
