Ukrainian forces went on the offensive in the Kursk region of Russia, Ukrainian and Russian officials said Sunday, in what appeared to be an effort to regain the initiative there as they struggle to thwart relentless Russian assaults across eastern Ukraine.
The Russian Ministry of Defense said Ukrainian forces launched a large assault featuring tanks, mine-clearing equipment and at least a dozen armored vehicles, and it claimed to have thwarted the attack. After Ukrainian forces unexpectedly attacked Kursk last summer, they took about 500 square miles of territory that Russia has been slowly clawing back.
Andrii Kovalenko, a senior Ukrainian government official focused on Russian disinformation operations, issued a statement referring to the Kursk region, saying that “the Russians are very worried because they were attacked on several fronts and it was a surprise for them.”
Ukrainian soldiers fighting in the area who were reached by phone declined to discuss ongoing operations beyond saying that Ukraine was on the offensive in parts of the Kursk region and that fierce fighting was raging there.
It was not possible to verify the claims by either side independently, and the scope of the Ukrainian assaults remained unclear.
Military analysts said that the attacks could be a deliberate attempt at misdirection, forcing Russian forces to react to one part of the front in the hopes of weakening them elsewhere.
Russian forces continue to make costly but consistent gains in the Donetsk region in eastern Ukraine. They are steadily grinding down a pocket of resistance around the town of Kurakhove in the southern Donbas region and are also fighting to envelop the larger city of Pokrovsk to the north, Ukrainian soldiers and officials said.
They are now within one mile of a critical supply road leading to Pokrovsk, which had served as a vital logistics and transportation hub for Ukrainian forces in the region.
Some American officials initially expressed skepticism about the wisdom of Ukraine’s incursion last August, concerned that it might be a drain on already exhausted and undermanned brigades struggling to stabilize defensive lines.
But as Russian casualties mounted and Ukraine firmed up its positions in the area, some of those same American officials changed their assessments.
Ukraine’s military leadership has argued that forcing the Kremlin to expend valuable resources to Kursk prevented the Kremlin from sending tens of thousands of troops to bolster Russian assaults along other parts of the front.
Ukraine now holds less than half the territory it seized in the Kursk offensive last summer, but it has been defending what remains despite repeated waves of Russian counterattacks, including recent assaults bolstered by thousands of North Korean soldiers.
President Vladimir V. Putin of Russia has sought to downplay the significance of the Kursk incursion, which was the first ground invasion of Russia since the end of World War II.
While saying that it was the military’s “sacred duty” to expel Ukrainian forces, he recently declined to offer a timeline for when that might be accomplished.
“We will definitely drive them out,” Mr. Putin said at his annual news conference in December. “I cannot answer the question about a specific date right now.”
The Ukrainian president, Volodymyr Zelensky, said Moscow continues to pay a high price trying to push the Ukrainians out.
“Specifically, in battles today and yesterday near just one village — Makhnovka in the Kursk region — the Russian army lost up to a battalion of infantry, including North Korean soldiers and Russian paratroopers,” Mr. Zelensky said on Saturday night. A battalion is composed of between 600 and 800 soldiers.
It was not possible to verify his claim but the Pentagon recently said that North Korea is suffering mass casualties on the Kursk front, with more than 1,000 killed or wounded in just a few weeks.
RIA Novosti, a Russian state news agency, said that about 340 Ukrainian soldiers had been killed and wounded in Kursk the past 24 hours. The agency, citing the Russian Defense Ministry, did not mention Russian casualties.
Mr. Zelensky said that holding on to land in Kursk gives Kyiv a “very strong trump card” in any possible negotiations with Moscow.
President-elect Donald J. Trump has vowed to end the war rapidly once he takes office, without saying how.
Liubov Sholudko, Nataliia Novosolova and Valerie Hopkins contributed reporting.
