KYIV, Ukraine — The Kremlin on Thursday accused 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.

The exact circumstances of the reported attack in the Bryansk region were unclear, as was the strategic purpose of such an assault. The regional governor said two civilians were killed.

A priest performs a religious service on the place of a building that was demolished after being heavily damaged by an airstrike, one year ago, in memory of those killed in Borodyanka, Ukraine on Thursday. Vadim Ghirda/Associated Press

If confirmed, it would be another indication following drone attacks earlier this week that Kyiv may be intensifying 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 the 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 to tighten controls on Russia’s border with Ukraine.

While Russian war hawks have expressed dismay with what they see as Putin’s reluctance to declare martial law and launch 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 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.

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 described 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.

The group was founded in August and consists mostly of anti-Putin far-right Russian extremists who have links with Ukrainian far-right groups, according to Michael Colborne, a researcher for the investigative website Bellingcat.

Colborne said on Twitter that Ukrainian military intelligence “very likely” approved the incursion.

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.

Russia’s Federal Security Service said it acted together with the military to “eliminate armed Ukrainian nationalists who violated the state border.” The agency claimed later that the attackers had been pushed back into Ukraine “where a massive artillery strike was inflicted on them.” It was not possible to verify the claim.

Putin canceled a planned trip to southern Russia because of the attack. He is set to chair a weekly meeting of the Russian Security Council on Friday.

Asked by reporters whether the activity could warrant a change in the status of the conflict, Kremlin spokesman Dmitry Peskov said, “I can’t say for now.”

The raid in the Bryansk region followed a spate of drone attacks. On Tuesday, drones that the Kremlin said were launched by Ukraine flew deep inside Russian territory, including one that got within 100 kilometers (60 miles) of Moscow. The Russian Defense Ministry also said Wednesday that the military repelled a drone attack on Crimea.

In Ukraine’s southern city of Zaporizhzhia, three people were killed and six others were wounded early Thursday when a Russian missile hit a five-story apartment building, destroying several floors.

A Russian drone attack hit people standing in line for humanitarian aid in a village in southern Ukraine’s Kherson region, wounding nine people, including a 16-year-old, the regional administration said.

Ukrainian President Volodymyr Zelenskyy said Russia “wants to turn every day for our people into a day of terror,” adding that “evil will not reign in our land.”

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 centers.

The war largely slowed to a grinding stalemate during the winter months, although a fierce battle continued for control of Bakhmut, a key eastern stronghold where Ukrainian officials say they might strategically withdraw.

The Ukrainian military’s general staff reported that Russian forces “continue to advance and storm the city,” but Kyiv’s troops repelled some of the attacks. Capturing the city would not only give Russian fighters 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.

In other developments, U.S. Secretary of State Antony Blinken and Russian Foreign Minister Sergey Lavrov talked briefly Thursday at a meeting of top diplomats from the Group of 20 nations. It was the first high-level meeting in months between Russia and the U.S.

A senior U.S. official, who spoke to reporters on condition of anonymity to discuss the private conversation, said Blinken had “disabused” Lavrov of any idea that U.S. support for Ukraine is wavering.