The Ukrainian military said on Monday that it had shot down five Russian fighter jets in three days, one of the biggest weekly losses for the Russian air force since the war began and a rare bright spot for Ukraine, whose forces have faced setbacks since its failed monthslong counteroffensive this year.

But the news could be offset if Russia’s claim that it had seized full control of the eastern town of Marinka is true. Russian forces have gradually advanced over months of battle against Ukrainian troops there, but Ukraine denied that the town was entirely under Russian control.

Just days after claiming to have downed three Su-34 fighter-bombers on Friday, the Ukrainian military said it had destroyed two more jets on Sunday. The claims could not be independently verified.

Early on Tuesday morning, Ukraine’s air force claimed another victory, saying it had destroyed a Russian ship, the Novocherkassk. The account could not be independently verified. Sergei Aksyonov, the Russia-installed head of Crimea, said that Ukrainian forces had attacked the Crimean Black Sea town of Feodosia, starting a fire in its port.

Military analysts, as well as several Ukrainian officials, have suggested that western-supplied Patriot missile systems may have been used in attacks on the Russian planes — an unusual instance of the air defense systems, which have mostly been deployed to shoot down incoming missiles, being used against aircraft.

Celebrating the Monday announcement, President Volodymyr Zelensky said, “This Christmas sets the right mood for the whole next year.”

The same day, Russia said it had taken the few blocks in Marinka that remained under Ukrainian control. Despite being largely reduced to rubble after months of shelling, Marinka holds some strategic value because it’s a key Ukrainian fortification on the eastern front.

Still, Ukraine has had time to build fallback positions in case the town falls and has vowed to thwart Russia’s efforts to advance to the borders of the Donetsk region, which it claimed to have annexed last year. The assault on Marinka was part of an offensive push that Moscow has launched in recent months all along the eastern front, and its capture could deal a blow to Ukrainian morale.

“Our troops have the opportunity to establish a wider operational area,” Russian President Vladimir Putin said in a video of a conversation between him and Russian defence minister Sergei Shoigu, during which Shoigu told Putin that Marinka had been captured.

New York Times News Service