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.
Military analysts, as well as several Ukrainian officials, have suggested that Western-supplied Patriot missile systems may have been used to target the warplanes — an unusual instance of the air defense systems, which have mostly been deployed to shoot down incoming missiles, being used against aircraft.
Celebrating the announcement, President Volodymyr Zelensky of Ukraine said on Monday, “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,” Mr. Putin said in a video of a conversation between him and Russian defense minister Sergei Shoigu, during which Mr. Shoigu told the Russian president that Marinka had been captured.
But Oleksandr Shtupun, a spokesman for the Ukrainian military, denied Russia’s claim to now have full control of Marinka, saying on national television that Ukrainian forces “are within the city.”
Russia has seized the initiative on much of the battlefield, and delays in the delivery of much-needed military aid caused by political wrangling in Washington have reportedly forced some Ukrainian units to scale back operations.
Although Russia has not been able to achieve air supremacy throughout Ukraine, the size of its air fleet dwarfs that of Ukraine’s and has been a driving force behind Moscow’s regular bombing of Ukrainian army positions, alongside attacks from Black Sea warships and field artillery. The downing of the jets could ease the pressure on Ukrainian troops operating in the hot spots of the fighting, analysts said, such as near the southern city of Kherson.
On Monday, Yurii Ihnat, a spokesman for Ukraine’s Air Force, said on national television that Russia “was no longer actively fighting in the Kherson region, realizing that there could be a trap for them” and had instead launched a dozen drones in the area to try to identify the system that shot down the planes.
The Su-34 jets are Russia’s modern fighter bombers, with the ability to hit distant targets while carrying several tons of bombs and missiles. They have been repeatedly used to strike Ukrainian forces with powerful glide bombs, which are guided airdropped munitions capable of flying long distances.
Ukrainian officials said that an Su-34 destroyed on Sunday was operating near the southern Russian-occupied city of Mariupol, while the location of another Su-30 jet that was downed is unknown.
The three warplanes downed on Friday were operating near the southern city of Kherson, authorities said, from which Ukraine has launched daring but deadly operations to secure a bridgehead on the Russian-controlled eastern bank of the Dnipro River.
In response, Russian forces bombarded the area, including Kherson, which is on the opposite bank and in Ukrainian hands. Local authorities said that three civilians were killed in the shelling of residential buildings on Sunday.
Mr. Ihnat told Ukrainian television that the Russian jets had been flying close to Ukrainian defense positions, trying to hit them with guided bombs, when they were shot down.
“They took a risk,” Mr. Ihnat said, “without success.”
Although Ukraine has not officially confirmed how the five warplanes were downed, Mykola Bielieskov, a military analyst at the National Institute for Strategic Studies, a Ukrainian government research group, said that U.S.-designed Patriot systems — America’s most advanced ground-based air-defense system — may have been involved in the operation.
The Patriot can shoot down incoming missiles before they hit their intended targets, as well as engage aircraft up to about a hundred miles away.
Mr. Bielieskov said Ukraine had already used the system to shoot down five Russian aircraft in May over Russia’s Bryansk region, as Mr. Ihnat told the Ukrainian media recently.
Ukrainian army officials also hinted at the use of Patriot systems in destroying the jets.
On Friday, Ukraine’s Air Force commander Mykola Oleshchuk published a screenshot of a Russian article referring to President Vladimir V. Putin’s statement last year that the Russian army would destroy the Patriot systems. “Coincidence. I don’t think so,” Mr. Oleshchuk wrote on the Telegram messaging app.
The next day, Mr. Ihnat published a message on Facebook that included emojis representing a skull and crossbones, three planes, and a picture of a Patriot system. “That’s exactly what gives us confidence and good mood,” he said.
The Russian authorities made no mention of the incidents, although they said on Sunday that their military had shot down four Ukrainian jets, a claim which could not be independently verified.
But the Fighterbomber Telegram channel, believed to be run by Capt. Ilya Tumanov of the Russian Army, reported on Friday the loss of an unspecified number of Russian warplanes, saying they had been downed by Patriot missiles.
When Ukraine first received some Patriot systems earlier this year, they were in short supply and were mostly used to protect Kyiv against Russian attacks, and in that role, they have proved very successful.
Since then, there have been more deliveries of the sophisticated system, including one earlier this month from Germany. Mr. Bielieskov said that some systems may now have been deployed at sites near the frontline, including on the southern front, “as a cover for land groupings of forces.”
Ukraine has been highly secretive about the use of Western air defenses out of concern that the Russian army would target them.
Mr. Zelensky said during a news conference last week that Ukraine would receive several additional Patriot systems this winter, without specifying a number. “We are getting stronger, more powerful,” he said.
Valeriy Romanenko, a Ukrainian aviation expert, told Ukrainian radio on Saturday that the presence of Patriot systems on the southern front would make the situation safer for Ukrainian troops.
“Now this number of raids with KABs will decrease,” Mr. Romanenko said, using the name for the guided bombs fired by Russian jets. The Russians would have to “carefully prepare each operation, check whether there is a Patriot nearby,” he added.
Nataliia Novosolova and Ivan Nechepurenko contributed researching.