Russian officials accused Ukrainian saboteurs on Thursday of crossing into western Russia and attacking local villages, an accusation that Ukraine denied and alleged would be used by Moscow to step up attacks.
The exact circumstances of the incident reported in the Bryansk region were unclear, including what the strategic purpose of such an attack would be.
If confirmed, it would be another indication following drone attacks earlier this week that Kyiv could be stepping up pressure against Moscow by exposing Russian defensive weaknesses, embarrassing the Kremlin and sowing unease among Russian civilians.
The announcement itself was a worrying development since it could be used by Russian authorities to step up its attacks in Ukraine in retaliation, as the war extends into its second year.
Ukrainian Presidential adviser Mykhailo Podolyak described the Russian reports as “a classic deliberate provocation.”
Russia “wants to scare its people to justify the attack on another country (and) the growing poverty after the year of war,” he tweeted, suggesting that the attack was the work of Russian partisans.
Amid conflicting initial reports, Russia’s Federal Security Service said fighting with the sabotage unit was taking place in the Bryansk region.
The Federal Security Service was quoted by the Russian state Tass news agency as saying that “activities to eliminate armed Ukrainian nationalists who violated the state border” were underway.
Tass, citing Russian law enforcement, reported earlier that the saboteurs were holding up to six people hostage. The local governor said the group had fired on a vehicle there, killing one man and wounding a 10-year-old child.
Drones that the Kremlin said were launched by Ukraine flew deep inside Russian territory on Tuesday, including one that got within 100 kilometres (60 miles) of Moscow.
Thursday's apparent incursion was also embarrassing for Russian President Vladimir Putin, coming days after he ordered the Federal Security Service to tighten controls on Russia’s border with Ukraine.
Kremlin spokesman Dmitry Peskov said that Mr. Putin canceled a planned trip to southern Russia set for Thursday and was receiving reports on the situation from the regional governor. Details of the alleged attack were still being clarified, he said.
Tass reported, citing an unnamed security official, that two villages in the Bryansk region — Sushany and Lyubechane — were under attack by “several dozen armed fighters.”
Alexander Bogomaz, the governor of the Bryansk region, which borders Ukraine, said the group fired on a vehicle in Lyubechane, killing one man and wounding a child. He also said that a Ukrainian drone struck a house in the Sushany, setting it ablaze.
In Ukraine on Thursday, three people were killed and six others were wounded when a Russian missile hit a five-story apartment building in a southeastern city.
Ukrainian President Volodymyr Zelenskyy said that several floors of the building were destroyed in the strike, which occurred while it was still dark.
The State Emergency Service said in an online statement that it had rescued 11 people so far.
Zaporizhzhia is a large city that had a population of more than 700,000 before Russia’s full-scale invasion of its neighbour just over a year ago. It's the administrative capital of the partially occupied Zaporizhzhia region, which is home to Europe’s largest nuclear plant.
Russian artillery, drones and missiles have pounded Ukrainian-held areas in the country’s south and east for months. Moscow denies aiming at civilian targets, but its indiscriminate shelling has wrought wide destruction in urban centres.
The war largely slowed to a grinding stalemate during the winter months.
Mr. Zelenskyy said Russia “wants to turn every day for our people into a day of terror.” He added: “But evil will not reign in our land.”
Meanwhile, a fierce battle continued for control of Bakhmut, a key eastern stronghold where Ukrainian officials say they might strategically withdraw.
Ukraine’s General Staff reported that the Russian forces “continue to advance and storm the city,” but Kyiv’s troops repelled some of the attacks on the ruined city. Donetsk regional Gov. Pavlo Kyrylenko reported that one person was wounded in Bakhmut on Thursday morning.
Bakhmut was among cities and villages in the Donetsk region that came under Russian shelling, according to the General Staff update.
Taking the city wouldn't only give the Russian forces a rare battlefield gain after months of setbacks, but it might rupture Ukraine’s supply lines and allow the Kremlin’s forces to press toward other Ukrainian strongholds in Donetsk.