Fierce Fighting Flares Around Eastern Ukrainian Town of Avdiivka

Russian and Ukrainian forces were locked in fierce fighting around the eastern frontline town of Avdiivka for a fourth straight day on Friday, in one of Moscow’s biggest military offensives in months.

Ukraine’s top military command said that it had repelled more than 20 attacks over the past day around the town, a linchpin of regional defenses whose capture by Russia would ease the way to the nearby, larger cities of Pokrovsk and Kostiantynivka.

Local officials described round-the-clock fighting and residential buildings that had been reduced to rubble by shelling, with heavy bombardments and the deployment of large numbers of troops and tanks by Russian forces.

“It was a hot night in Avdiivka,” Vitaliy Barabash, the head of the town’s military administration, told Ukrainian television. “The assaults do not stop, day or night.”

The attack on Avdiivka, which is toward the southern end of the eastern front line and has already been devastated by Russian shelling during the war, may indicate that Moscow is trying to regain the initiative on the battlefield, after months on the defensive after Kyiv launched its counteroffensive this summer in the south.

“The enemy sees Avdiivka as an opportunity to gain a significant victory and turn the tide of hostilities,” Oleksandr Shtupun, a spokesman for Ukraine’s southern forces, said on Thursday.

But as much as Ukrainian forces have struggled to break through Russia’s formidable defensive lines in the south, it will not be easy for Russian troops to overrun Kyiv’s heavily fortified positions around Avdiivka, which has been on the front line since Russian-backed militants seized territory in eastern Ukraine, including the nearby city of Donetsk, in 2014.

The government in Kyiv has warned in recent months that Moscow was massing troops and equipment in eastern Ukraine, where Russia claims to have annexed the regions of Luhansk and Donetsk, even though it does not fully control them.

The attack on Avdiivka has coincided with Russian ground troop assaults near Kupiansk, another frontline town in the east, local officials said.

To what extent these attacks may prove conclusive remains to be seen. Frontline combat this year has mostly been characterized by bloody fighting that has yielded few territorial gains on either side.

Ukrainian officials said that up to three Russian battalions had been involved in the assault on Avdiivka, supported by tanks and armored vehicles.

“The Russians threw a lot of forces in this direction. They are betting on quantity,” Andriy Yermak, the head of the Ukrainian president’s office, said on X, the social media platform formerly known as Twitter.

The Institute for the Study of War, a Washington-based think tank, said that geolocated footage indicated that Russia had likely lost dozens of armored vehicles since the start of the assault, for territorial gains of less than two square miles.

Mr. Barabash said Russian forces were trying to encircle Avdiivka, which sits in a strategic pocket surrounded to the north, east and south by Russian positions.

He reported intense fighting to the north and south of the town, adding that one civilian had been killed and several others wounded over the past day.

But encircling Avdiivka would most likely require more forces than Russia has committed to its offensive in the area so far, according to the Institute for the Study of War.

Over time, Avdiivka has become a symbol of resistance to Russia’s onslaught. It withstood eight years of low-intensity warfare in eastern Ukraine before the full-scale invasion began in February 2022, and now a year and a half of enormous assaults by the Russian Army, which have left the town in ruins and forced almost all of its 30,000 inhabitants to flee.

Ukrainian forces have held out through airstrikes and continual artillery bombardment, using the grounds of a coking coal factory as a fortress and digging trenches and bunkers around the area.

“Avdiivka. We are holding our ground,” President Volodymyr Zelensky of Ukraine wrote on the Telegram messaging app on Thursday.

Beyond the eastern front line, fighting continued in other parts of the country on Friday. The Ukrainian military said it had blown up a strategic railway line in Russian-occupied territory in the south and attacked a patrol ship in the Black Sea, which has recently become a new hot spot in the war.

But any damage to the Russian ship, the Pavel Derzhavin, remained unclear on Friday. Dmytro Pletenchuk, a spokesman for the Ukrainian Navy, told the Ukrainian media that the ship was able to leave the scene of the attack. There was no immediate comment from the Russian military.