NORTHERN UKRAINE — Fresh from leading a military incursion across Russia’s border, commanders of anti-Kremlin armed groups taunted the Russian Army on Wednesday for its slow response and threatened Moscow with more to come.
Russia, they told reporters at a news conference in a forest in northern Ukraine near the Russian border, should brace for further cross-border assaults, warning that any section of the frontier could be vulnerable.
By Wednesday, the incursion was over, the fighters said, and the news conference back in Ukraine seemed intended as a victory lap to highlight weaknesses in the Russian military and to try to shape the narrative of the fighting.
Military analysts suggested the cross-border attack this week was aimed at forcing Russia to divert troops for border defense from the front in southeastern Ukraine ahead of a planned Ukrainian counteroffensive, and to embarrass President Vladimir V. Putin’s government.
Images verified by The New York Times showed armored vehicles with Ukrainian markings driving in the Belgorod region of southern Russia and smoke from explosions billowing over farm fields. Two groups calling themselves armed Russian opposition organizations, the Free Russia Legion and the Russian Volunteer Corps, claimed responsibility.
The raid was the most disruptive, direct ground assault on Russian territory during the war, staged from an area of northern Ukraine that the Ukrainian Army freed from Russian occupation last spring. Kyiv denied directing the assault and said only Russian citizens crossed the border in the raid.
The commanders and soldiers stood, toting machine guns, some with camouflage fabric bands pulled over their faces, in front of an armored personnel carrier that they said they had captured and driven out of Russia. That could not be independently confirmed.
They called the two-day incursion a success. “We saw the military and political leadership of Russia are absolutely not prepared” for an attack, the commander said. “When it came to action, everything fell apart.”
Analysts of Russian politics said the attack could stir discontent over Russian military capabilities among the country’s pro-war groups but could also help Mr. Putin with a rally-around-the-flag effect. Already, the Kremlin has said that the raiders had abandoned American-made military vehicles inside Russia, and Moscow can use the far-right histories of some of the raiders to bolster its largely false claim to be fighting Nazis in Ukraine.
The Kremlin, eager to discredit the renegade Russians, dismissed them on Wednesday as neo-fascists.
One commander of the Russian Volunteer Corps, Denis Kapustin, is a known far-right extremist. The Anti-Defamation League has said that he was involved in the Mixed Martial Arts world in Europe and that he has trained younger members of the far-right National Democratic Party of Germany. At the news conference on Wednesday, he introduced himself to reporters by his call sign, White Rex.
Asked about his ultranationalist ideology Mr. Kapustin described himself as right wing and said that his views were “traditionalist” and “patriotic.”
Sergei K. Shoigu, Russia’s defense minister, called the raid a terrorist act. “In response to similar action by Ukrainian fighters, we will respond in an operational manner and very harshly,” he told a gathering of security officials in Moscow, Russian media reported on Wednesday.
The Ukrainian military, he said, had been aware of the groups’ intentions ahead of the raid, helped in the planning, and provided gasoline for vehicles and medical care for wounded soldiers.
“Everything we do within the state borders of Ukraine we obviously coordinate with the Ukrainian military,” he said. “Everything we do, every decision we make, beyond the state border, is our decision.”
The Ukrainian military, he said, had “wished us good luck” but not crossed the border into Russia, echoing what Ukrainian officials had said.
Another commander, who asked to be identified by the nickname Cesar, said Russia’s military had been slow to respond with reinforcements after the group drove armored personnel carriers across the border and attacked a border post. “The reaction was slow, panicked, disorganized and didn’t begin for hours,” he said.
Cesar said the Free Russia Legion had driven American-made armored vehicles but said they were not provided by the Ukrainian military. The group had bought them, he said. He said his group suffered losses in the fighting but declined to say how many soldiers had been killed or wounded.
White Rex said his group, the Russian Volunteer Corps, had not used any American-made vehicles in the assault.
The news conference organizers kept a strict time limit, lest the gathering be targeted by a Russian missile. After about 40 minutes, the soldiers drove away in pickup trucks and, with a rumble of a diesel engine, the armored personnel carrier they said they had captured.
Evelina Riabenko contributed reporting.
