Anti-Putin Russians say they launched a cross-border attack from Ukraine. Here's what we know

An apparent attack on Russian soil by anti-Putin Russians, fighting in support of Ukraine, has sparked confusion and anger in Moscow.

Residents of the settlements under attack in Russia's Belgorod region have been resettled in other areas as authorities continue "clearing the territory" after the cross-border incursion that launched in Ukraine, officials said on Tuesday.

One civilian died as a result of the fighting, according to regional governor Vyacheslav Gladkov.

But questions linger about the group behind the attack, how it took place, and what it means for the war.

Here's what you need to know.

The two groups of anti-Putin Russian nationals, who are fighting in Ukraine as part of Kyiv's defense forces, the Freedom for Russia Legion and Russian Volunteer Corps, claimed responsibility for the attack in Russian's southwestern region of Belgorod, which borders north-eastern Ukraine.

"Residential and administrative buildings and civilian infrastructure were subjected to mortar and artillery fire. As a result of these criminal actions, several civilians were wounded," Russia's Investigative Committee said on Telegram as it announced an investigation into the attack.