The four members of the Brotherhood Battalion later buried in Kyiv were Yurii Horovets, 34, Taras Karpiuk, 38, Maksym Mykhailov, 32 and Bohdan Liagov, 19.
Ukrainian authorities did not comment on the raid then, and have subsequently denied involvement in attacks claimed by Ukrainian-based groups on Russian soil.
"Our aim is to bring the war over to Russian territory.
"When we are on Russian territory, we act autonomously," he added.
Ukraine's defence ministry did not immediately respond to a request for comment on its relationship with the Brotherhood Battalion, called "Bratstvo" in Ukrainian, and the armed forces.