A group of fighters aligned with Ukraine, which earlier this week engaged in the most intense fighting inside Russia’s borders since the invasion, gathered foreign and local press at an undisclosed location on Wednesday to celebrate, taunt the Kremlin and display what they called “military trophies” from their foray into their homeland: Russia.

Their leader, Denis Kapustin, was proud that his force of anti-Putin Russians at one point controlled, he said, 42 square kilometers, or 16 square kilometers, of Russian territory.

“I want to prove that it is possible to fight a tyrant,” he said. “That Putin’s power is not unlimited, that the security services can beat, control and torture unarmed people. But as soon as they encounter fully armed resistance, they flee.”

It was the rhetoric of a dissident freedom fighter, but there was an adversarial tone that stood out as clearly as the neo-Nazi Black Sun patch on one of the soldiers’ uniforms: Mr. Kapustin and prominent members of the armed group he leads, the Russian Volunteer Corps, openly espouse far-right views. In fact, German officials and humanitarian groups, including the Anti-Defamation Leaguehas identified Mr. Kapustin as a Neo-Nazi.

Mr. Kapustin, who has long used the alias Denis Nikitin but usually 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 football fans and later became “one of the most influential activists” in a neo-Nazi splinter group in the mixed martial arts sceneofficials in the German state of North Rhine-Westphalia have said.

Mr. Kapustin has reportedly been prohibited from entering Europe’s 27-country visa-free Schengen zone, but he has only said that Germany canceled his residence permit.

The fact that the group has gained attention for its activities and revived coverage of the group’s ties to neo-Nazis is a troubling development for Ukraine’s government, especially since Russian President Vladimir V. Putin has justified his invasion with the false claim of fighting neo-Nazis. -Nazis and made it a regular theme of Kremlin propaganda.

Most of the anti-Russian groups harbor long-term political ambitions to return home and overthrow the Russian and Belarusian governments.

“The Russian Volunteer Corps marches in and destroys the current government – that’s the only way,” Mr. Kapustin said earlier this year. “You cannot persuade a tyrant to leave, and any other force would be seen as an intruder.”

In reality, far-right groups in Ukraine are a small minority, and Ukraine has denied any involvement in the Russian volunteer corps or any role in the fighting on the Russian side of the border. But Mr. Kapustin said his group “definitely received a lot of encouragement” from the Ukrainian authorities.

Some on Russia’s far right have long mourned Putin, particularly for his jailing of so many nationalists, but also for his policies on immigration and for what they perceive as giving too much power to minorities such as ethnic Chechens. Since the 2014 Maidan revolution and the start of the war between Ukraine and Russian-backed separatists in the eastern Donbas region, many of them have made a home in Ukraine and are now fighting on the side of their adopted country.

The Russian Volunteer Corps, also known by its Russian initials RDK, was one of two groups of anti-Russian fighters that carried out a cross-border attack in the Belgorod region of southern Russia on Monday, engaging enemy troops in two days of skirmishes.

The purpose of the incursions, the groups say, was to force Moscow to redeploy troops from occupied areas of Ukraine to defend its borders, stretching its defenses ahead of a planned Ukrainian counteroffensive, a goal that aligns with the broader goals of Ukraine’s military.

The Russian Volunteer Corps also took credit for two incidents in the Russian border region of Bryansk in March and April.

The other group was Free Russian Legion, which operates under the umbrella of the Ukrainian International Legion, a force that includes American and British volunteers, as well as Belarusians, Georgians and others. It is overseen by the Armed Forces of Ukraine and led by Ukrainian officers.

At the press conference on Wednesday, Kapustin confirmed that his group was not controlled by the Ukrainian army, but said the military had wished the fighters “good luck”. There had been “nothing beyond encouragement” from the Ukrainian side, he said.

“Everything we do, every decision we make, across state lines is our own decision what we do. Of course we can ask our peers and friends for their help in planning,” he continued. “They would say ‘yes, no’ and this is the kind of encouragement, help I was talking about.” That claim could not be independently verified.

Andriy Chernyak, a representative of Ukraine’s military intelligence service, defended Kiev’s willingness to let the group fight on its behalf.

“Ukraine definitely supports all those who are ready to fight Putin’s regime,” he said, adding: “People came to Ukraine and said they want to help us fight Putin’s regime, so of course we let them, like many others. people from foreign countries.”

Ukraine has called the incursions an “internal Russian crisis” given that the members of the group are themselves Russians.

Some analysts dismissed the importance of the RDK as a fighting force even as they warn of the dangers they pose. 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 entity.

“They’re largely a far-right group of neo-Nazi exiles making these incursions into Russian-held territory who seem far more concerned with creating content on social media than anything else,” Colborne said.

Some other members of the RDK who were photographed during the border raid have also publicly adopted neo-Nazi views. A man, Aleksandr Skachkov, was arrested by Ukrainian security services in 2020 for selling a Russian translation of the white supremacist manifesto of the shooter in Christchurch, New Zealandwhich killed 51 mosque worshipers in 2019. Mr. Skachkov was released on bail after spending a month in jail.

Another member, Aleksei Levkin, who filmed a selfie video with the RDK designation, is a founder of a group called Wotan Youth which 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 to 2019.

Pictures posted online of the fighters earlier this week showed them posing in front of captured Russian gear, with some wearing Nazi-style patches and equipment. One note depicted a hooded member of the Ku Klux Klan.

Colborne said the images of Kapustin and his fighters could damage Ukraine’s defenses by making allies wary that they could support armed far-right groups.

“I’m worried that something like this could backfire on Ukraine because there are no ambiguous people,” he said. “These are not unknown people, and they are not helping Ukraine in any practical sense.”

Mr Kapustin, who in addition to speaking Russian is fluent in English and German, told reporters he did not think it was an “accusation” to be called “extreme right”.

“We have never hidden our views,” he said. “We are a right-wing, conservative, military, semi-political organization,” he said.

Thomas Gibbons-Neff, Andrew E. Kramer and Oleg Matsnev contributed reporting.