Russia alleges that dozens of Ukrainian militants crossed into one of its border towns in its Belgorod region, striking targets and forcing an evacuation, before over 70 of the attackers were killed or pushed back by what the authorities termed a counterterrorism operation.

Ukraine denied any involvement in the skirmishes Monday and Tuesday, instead blaming two Russian groups that claim to be volunteers fighting alongside Kyiv's forces in an uprising against the government of President Vladimir Putin.

While neither version could be independently verified, whatever happened appears to have sent Moscow scrambling to respond to one of the most serious border incursions since Putin launched the invasion of Ukraine in February 2022.

Belgorod Gov. Vyacheslav Gladkov said an elderly woman died in the chaotic evacuation, and 12 people were wounded in the attack and shelling. As fighting there apparently continued Tuesday morning, he urged residents not to return to their homes, and only in late afternoon declared the operation was over.

A look at what's known about the attack and the murky groups who say they carried it out:

Who's claiming responsibility?

Two groups — the Freedom of Russia Legion and Russian Volunteer Corps – claimed responsibility for the attack and announced an ambitious goal of “liberating” the Belgorod region. Little is known about them beyond what they say about themselves, and it's not clear how they are.

The website of the Freedom of Russia Legion says it was formed last spring “out of Russians’ desire to fight against Putin’s armed gang” and is “officially recognized” by Kyiv’s military. “We are fighting in full cooperation with the Armed Forces of Ukraine and under the leadership of the Ukrainian command,” the website says.

The website said it fought last summer in “small battle groups,” and now was involved in the battle for the eastern city of Bakhmut.

The Russian Volunteer Corps’ page in the messaging app Telegram used to say it was a formation within the Armed Forces of Ukraine. It now describes itself as merely fighting on the Ukrainian side.

In August 2022, an announcement posted there said: “We, Russian volunteers living in Ukraine, decided to take up arms and create a military formation, the Russian Volunteer Corps, in order to together with our Ukrainian comrades defend their homeland which gave us shelter, and then continue the fight against the criminal Putin regime and his henchmen.”

Other posts claimed the group was fighting in southeastern Ukraine, or as volunteers serving elsewhere in the country, including in Kyiv's suburbs of Bucha and Irpin.

In March, the Russian Volunteer Corps claimed responsibility for an incursion in Russia's Bryansk region, another border area. Media reports at the time identified some of its members as Russian nationalists.

In a post Tuesday, the Russian Volunteer Corps described its political views as “right-wing conservative and traditionalist."

What does Ukraine say?

Ukrainian officials have never confirmed any ties with either group. The government in Kyiv denied involvement in this week's Belgorod incident, calling it an act by disgruntled Russians.

When they did talk about it, officials were vague. Deputy Defense Minister Hanna Maliar said “patriots of Russia” and “people who actually rebelled against Putin’s regime” were behind the attack. Presidential adviser Mykhailo Podolyak blamed “underground guerrilla groups” that are “composed of Russian citizens.”

In remarks to the news outlet Suspilne, Ukraine intelligence official Andrii Yusov said it was the Russian Volunteer Corps and the Freedom of Russia Legion.

Andrii Cherniak, another intelligence representative pointed to the fact that the two groups claimed responsibility. "This is the consequence of aggressive politics of Putin’s regime and Russia’s invasion of Ukraine,” he told The Associated Press.

What does Russia say?

Russia calls it an incursion by saboteurs deployed by Kyiv, with officials and state media using various epithets ranging from “militants” to “terrorists.”

Kremlin spokesman Dmitry Peskov said the Belgorod attack was a diversion, meant “to draw attention away” from Russia's victory in the eastern Ukrainian city of Bakhmut, which Moscow claimed to have captured over the weekend after months of bloody fighting.

Asked Tuesday about claims that the invaders were ethnic Russians, Peskov insisted that “these are Ukrainian militants from Ukraine.”

“There are lots of ethnic Russians in Ukraine, but these are still Ukrainian militants,” Peskov said.

Defense Ministry spokesman Igor Konashenkov said more than 70 “Ukrainian terrorists” were killed in Russia’s operation. He also referred to the attackers as “nationalists.”

Russian state TV reported the invaders were from Ukraine's armed forces. One report alleged the attackers used U.S. military equipment despite Washington’s assurances its weapons won't be used for attacks on Russia.

What's the truth?

It's hard to know. Analysts and commentators say both Russia and Ukraine would likely benefit from its own version of the events.

The British Defense Ministry tweeted Tuesday that “Russia will almost certainly use these incidents to support the official narrative that it is the victim in the war.”

Russian state media coverage appears to support this notion, with its allegations that U.S. weapons were used in the attack and the general tone of some reports that overlaid video from the region with tense, dramatic music.

For Kyiv, it's beneficial “to take up the position of an observer and not admit its involvement,” said Ukrainian military analyst Oleh Zhdanov.

“The fact is that the war is happening on Russian territory, the Kremlin is being clearly indicated that Russians are not the only ones who can employ hybrid (warfare) methods,” Zhdanov told AP.

The involvement of the Russian Volunteer Corps and the Freedom of Russia Legion should serve as signs that “there are forces inside Russia who can resist Putin’s regime,” he said.

At the same time, the Belgorod attack “showed Russia’s helplessness," Zhdanov said.

“Russia turned out to be completely unprepared -– neither its security forces, nor border guards, nor special services were prepared for hostilities on their own turf. The myth that Russia keeps its border locked has been busted,” he added.

Some Russian voices echoed that sentiment. Yevgeny Prigozhin, head of the Wagner private military contractor, used the incident as yet another chance to bash the Russian Defense Ministry for not adequately protecting the border.

Alexander Kots, military correspondent with the pro-Kremlin newspaper Komsomolskaya Pravda, also raised questions on his Telegram page.

“What’s with our technical equipment of the border, surveillance systems, motion detection systems?" he asked. "What’s with mining of the potentially dangerous areas? What’s with anti-tank equipment? Why did an enemy armored group breach deep into our territory?”

These are the questions “to which there are no answers,” Kots said. “To be more accurate, there are, but they’re very unpleasant.”