One of the anti-Kremlin groups responsible for an armed incursion into Russia this week, the Russian Volunteer Corps, is led by a far-right extremist described by German officials and humanitarian groups, including the Anti-Defamation League, as a neo-Nazi.
The Volunteer Corps, made up of Russians who oppose Vladimir V. Putin’s war, does not have any public affiliation with the Ukrainian Army. But the group’s claims to be fighting for Ukraine’s cause present an uncomfortable situation for the government in Kyiv. President Vladimir V. Putin of Russia has falsely claimed that his country is fighting Nazis as a pretext for his country’s invasion, a regular theme of Kremlin propaganda.
The commander of the corps — Denis Kapustin, who has long used the alias Denis Nikitin, but typically goes by his military call sign, White Rex — is a Russian citizen who moved to Germany in the early 2000s. He associated with a group of violent soccer fans and later became, according to officials in the German state of North Rhine-Westphalia, “one of the most influential activists” in a neo-Nazi splinter of the mixed-martial-arts scene.
He has been barred from entering Europe’s visa-free 27-country Schengen zone.
The Volunteer Corps, known by its Russian initials R.D.K., also claimed credit for two incidents in the Russian border region of Bryansk in March and April. Ukrainian authorities have publicly denied any role in the fighting on the Russian side of the border.
The Russian Volunteer Corps was one of two groups of Russian fighters that conducted a cross-border attack in the Belgorod region of southern Russia that began on Monday, engaging Russian troops over two days of skirmishing. The aim of the incursions, the groups say, is to force Russia to redeploy soldiers from occupied areas of Ukraine to defend its borders, as Ukraine prepares for a counteroffensive.
The second group was the Free Russia Legion, which operates under the umbrella of Ukraine’s International Legion, a force that includes American and British volunteers, as well as Belarusians, Georgians and others. It is overseen by Ukraine’s Armed Forces and commanded by Ukrainian officers. Several hundred Russian fighters have been deployed to the front lines in eastern Ukraine, officials said.
At a joint news conference with the Free Russia Legion on Wednesday, Mr. Kapustin said his group was not under the control of the Ukrainian Army, but that the military had supported his fighters with information, gasoline, food and medical supplies, along with the evacuation of wounded personnel. That claim could not be independently verified.
Andriy Chernyak, a representative of Ukraine’s military intelligence service, said that he did not have any information about possible material support the Ukrainian military may have given to members of the R.D.K., but said that “Ukraine definitely supports all those who are ready to fight the Putin regime.”
“People came to Ukraine and said that they want to help us to fight Putin’s regime, so of course we let them, same as many other people from foreign countries,” Mr. Chernyak said.
Ukraine has called the incursions an “internal Russian crisis” given that the members of the group are Russians themselves, and the episode plays into a Ukrainian military objective of trying to force Russia to redeploy troops from the front lines to defend its borders.
Michael Colborne, a researcher at Bellingcat who reports on the international far right, said he was hesitant to even call the Russian Volunteer Corps a military unit.
“They are largely a far-right group of neo-Nazi exiles who are undertaking these incursions into Russian-held territory who seem far more concerned about making social media content than anything else,” Mr. Colborne said.
Some of the other members of the Russian Volunteer Corps photographed during the border raids also have publicly embraced neo-Nazi views. One man, Aleksandr Skachkov, was arrested by the Ukrainian Security Services in 2020 for selling a Russian translation of the white supremacist manifesto of the shooter in Christchurch, New Zealand, who killed 51 mosque worshipers in 2019.
Another one, Aleksei Levkin, who filmed a selfie video wearing the R.D.K. insignia, is a founder of a group called Wotanjugend that started in Russia but later moved to Ukraine. Mr. Levkin also organizes a National Socialist Black Metal Festival, which began in Moscow in 2012 but was held in Kyiv from 2014 until 2019.
Pictures posted online by the fighters earlier this week of volunteer corps members posing in front of captured Russian equipment featured some fighters wearing Nazi-style patches and equipment. One patch depicts a hooded member of the Ku Klux Klan and another shows a Black Sun, a symbol with a strong connection to Nazi Germany.
Mr. Colborne said the images of Mr. Kapustin and his fighters could do damage to Ukraine’s defense by making allies wary that they could be supporting far-right armed groups.
“I worry that something like this could backfire on Ukraine because these are not ambiguous people,” he said. “These are not unknown people, and they are not helping Ukraine in any practical sense.”
Thomas Gibbons-Neff contributed reporting from London and Oleg Matsnev from Berlin.