KYIV, Ukraine (AP) — Russian troops and security forces quashed Tuesday an alleged cross-border raid from Ukraine, claiming to have killed more than 70 attackers in a battle that lasted around 24 hours, a senior Moscow official said.

It was not possible to independently confirm claims about the armed incursion into Russian territory that began Monday. Nor was it possible to say with any certainty who was behind the attack or what its aims were.

Disinformation has been one of the weapons of the almost 15-month war.

Moscow blamed the raid on Ukrainian military saboteurs. Kyiv portrayed the incident as an uprising against the Kremlin by Russian partisans. It wasn’t immediately possible to reconcile the two versions.

The battle took place in the Belgorod region, about 80 kilometres (45 miles) north of the city of Kharkiv, in eastern Ukraine.

Russian Defense Ministry spokesman Igor Konashenkov claimed the armed attackers were routed by local troop units, air strikes and artillery fire.

“The remnants of the nationalists were driven back to the territory of Ukraine, where they continued to be hit by fire until they were completely eliminated,” Konashenkov said, without providing evidence. He did not mention any Russian casualties.

Four armoured combat vehicles and five pickup trucks used by the attackers were destroyed, he said. Local officials alleged drones and artillery were also used in the assault.

The governor of the Belgorod region, Vyacheslav Gladkov, said the raid targeted the rural area around the town of Graivoron, a town about five kilometres (three miles) from the border. Twelve civilians were wounded in the attack, he said, and an older woman died during the evacuation.

Earlier Tuesday, Gladkov urged residents who had evacuated to stay put and not return home until they received official instructions to do so. He said a “counterterrorism operation” was underway.

While it wasn’t the first time Russia has alleged an incursion by Ukrainian saboteurs, it was the first time the operation to counter the raid continued for a second day, highlighting the struggles Moscow is facing amid its bogged-down invasion of Ukraine and embarrassing the Kremlin.

Russian territory and Russia-occupied areas of Ukraine have also been hit by drones and explosions that have derailed trains, though Kyiv officials brush off accusations of orchestrating them.

Ukraine said that Russian citizens belonging to murky groups calling themselves the Russian Volunteer Corps and the “Freedom of Russia” Legion were behind the assault.

Russian dissidents unhappy about Russian President Vladimir Putin’s policies instigated the assault, Ukrainian Deputy Defense Minister Hanna Maliar said Tuesday.

“These are Russian patriots, as we understand it. People who actually rebelled against the Putin regime,” she said.

The “Freedom of Russia” Legion said in its Telegram channel that the goal was to “liberate” the region.

The Russian Volunteer Corps implied in a Telegram post that the attack was over, adding: “One day, we’ll come to stay.” The post went up at around the same time as the Russian defence ministry comment about quashing the assault.

The UK Defense Ministry said it was “highly likely” that Russian security forces were fighting partisans in at least three locations in Belgorod.

“Russia is facing an increasingly serious multi-domain security threat in its border regions, with losses of combat aircraft, improvised explosive device attacks on rail lines, and now direct partisan action,” it said in a tweet on Tuesday.

Russia’s Investigative Committee, its top law enforcement agency, announced an investigation into alleged terrorism and attempted murder in connection with the incident.

Belgorod officials earlier this year said they had spent nearly 10 billion rubles ($125 million; 116 million euros) on fortifications to protect the region from an incursion amid the war.

Kremlin spokesman Dmitry Peskov said the raid “elicits deep concerns,” and a “bigger effort” was required to prevent such attacks in the future.

Peskov refused to say how many attackers were involved in the assault, nor would he comment on why efforts to put down the attackers were taking so long. In a conference call with reporters Tuesday, he redirected those questions to Russia’s Defense Ministry and the Federal Security Service, or FSB.

Gladkov, the regional governor, said authorities imposed special controls, including personal document checks, and stopped the work of companies that use “explosives, radioactive, chemically and biologically hazardous substances.”

The Russian Volunteer Corps claimed to have breached the border in early March. The shadowy group describes itself as “a volunteer formation fighting on Ukraine’s side.” It’s not clear if it has any ties with the Ukrainian military. The same is true for the “Freedom of Russia” Legion.

The Belgorod region in southwest Russia, just like the neighbouring Bryansk region and several other areas, has witnessed sporadic spillover from the war, with its border towns and villages regularly coming under shelling and drone attacks.

Elsewhere, Ukrainian forces have made minor progress against Russian forces on the edge of Bakhmut, the eastern Ukrainian city that Moscow claims to have captured, according to Maliar, the Ukrainian deputy defence minister.

She said Tuesday that Ukrainian troops still controlled the southwestern outskirts of the city and that fighting was continuing in the suburbs, on Russia’s flanks.

Ukrainian military leaders say the fight in Bakhmut isn’t over.