Pentagon press secretary Pat Ryder held a news briefing on Thursday as the Kremlin accuses Ukrainian saboteurs of crossing into western Russia and firing on villagers. Ukraine denied the claim and warned that Moscow could use the allegations to justify stepping up its own attacks in the ongoing war.
Watch the briefing in the player above.
The exact circumstances of the alleged attack reported in the Bryansk region were unclear, including what the strategic purpose of such an assault might be.
If confirmed, it would be another indication following drone attacks earlier this week that Kyiv may be stepping up pressure against Moscow by exposing Russian defensive weaknesses, embarrassing the Kremlin and sowing unease among Russian civilians.
Russian President Vladimir Putin blamed Ukrainian "terrorists" for an incursion, claiming that they deliberately targeted civilians, including children in "yet another terror attack, another crime."
"They infiltrated the area near the border and opened fire on civilians," Putin said during a video call. "They saw a civilian vehicle with civilians, with children in it and they fired on them."
The alleged incursion came just days after Putin ordered the Federal Security Service, the main successor to the KGB, to tighten controls on Russia's border with Ukraine.
While Russian war hawks have expressed dismay about what they have seen as Putin's reluctance to declare martial law and a sweeping mobilization of soldiers, the Russian leader's comments Thursday did not appear to signal any such moves.
Putin blamed the attack on "neo-Nazis" and said it confirmed that Russia did the right thing by invading Ukraine. "I repeat again: They will not succeed and we will finish pushing them out," he said.
When he ordered the invasion, the Russian leader vowed to "denazify" Ukraine, alleging falsely that radical neo-Nazi groups dominate the country led by a Jewish president. Kyiv and its Western allies dismissed his assertion as a bogus cover for an unprovoked act of aggression.
Ukraine's military intelligence representative, Andrii Cherniak, saw the Russian claims as evidence that Moscow is facing what Kyiv says is an uprising among its own disgruntled people.
"This was done by the Russians; Ukraine has nothing to do with it," he told The Associated Press.
Cherniak noted that a group calling itself the Russian Volunteer Corps claimed it crossed the border into Russia in a video that also urged Russians to rebel. The group's statement did not explain what actions it took or what specific objectives it wanted to achieve.
The Russian Volunteer Corps describes itself as "a volunteer formation in the Armed Forces of Ukraine." Little is known about the group, and it was not immediately clear if it has any ties with the Ukrainian military.
Ukrainian presidential adviser Mykhailo Podolyak described the Russian claims 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 Russian partisans were behind what happened in Bryansk.
Bryansk Gov. Alexander Bogomaz said the attackers killed two civilians and wounded a child in the village of Lyubechane.