Some other members of the R.D.K. photographed during the border raid 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. Mr. Skachkov was released on bail after spending a month in jail.
Another member, 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 showed them posing in front of captured Russian equipment, with some wearing Nazi-style patches and equipment. One patch depicted a hooded member of the Ku Klux Klan.
Mr. Colborne said the images of Mr. Kapustin and his fighters could damage Ukraine’s defense by making allies wary 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.”
Mr. Kapustin, who in addition to speaking Russian speaks fluent English and German, told reporters he did not think being called “far right” was an “accusation.”
“We have never concealed our views,” he said. “We are a right, conservative, military, semipolitical organization,” he said.
Thomas Gibbons-Neff, Andrew E. Kramer and Oleg Matsnev contributed reporting.