The intensifying push is one of Russia’s few offensive operations in months, as it tries to seize land in Ukrainian regions it claims to have already annexed.
Russian forces have intensified attacks in recent days, targeting a string of towns along an eastern stretch of the front line even as they defend against a Ukrainian offensive in the south. Their movements add to the sense of inconclusive, back-and-forth fighting that has characterized frontline combat for weeks, with few territorial gains.
Ukraine’s military said on Wednesday that it had repelled tank attacks supported by artillery in one of Russia’s heaviest assaults in months on the city of Avdiivka, and that Russia had over the past 24 hours dropped 20 powerful aviation bombs near the cities of Lyman and Kupiansk, all in eastern Ukraine.
Ukrainian commanders had since last month cautioned that Russia was marshaling troops in the east for a renewed attempt to break through Ukrainian lines. The area was a focus of a Russian offensive last winter that largely failed.
“Our Avdiivka is under massive attacks by Russian artillery and aviation,” Andriy Yermak, the head of the Ukrainian president’s office, said on Tuesday in a post on the Telegram messaging service, which included a photo of a building reduced to rubble.
Mykola Bielieskov, a military analyst at the National Institute for Strategic Studies, a Ukrainian government research group, said in an interview that “the scale of the recent attacks is unprecedented” in Avdiivka. He compared it to the fighting that took place there more than half a year ago, when Russia relentlessly shelled the town during its winter offensive.
Russia’s attempts to advance this year have mostly taken place along Ukraine’s eastern front line, where Moscow is trying to capture Ukrainian territory in two provinces, Donetsk and Luhansk, that it has claimed to have annexed but that it does not fully control. Other eastern towns targeted by Russia include Bakhmut, which Wagner’s mercenaries captured in May.
Ukrainian forces have retaken several strategic villages in the east near Bakhmut. But with both sides holed up in heavily fortified positions, relatively little ground has changed hands this year anywhere along the front.
Still, Russian forces appeared to have deployed significant effort in manpower and weaponry in its push to close in on Avdiivka and Kupiansk.
Ilya Yevlas, a spokesman for the Ukrainian army in the east, told Ukrainian television on Wednesday that Russia had amassed troops to assault Kupiansk from the east, with an intermediary goal of pushing Kyiv’s forces from the eastern bank of the Oskil River. Kupiansk is on the river’s western bank.
Even if they accomplished that, military analysts have said, a cross-river assault on the town is unlikely, in part because success would position Russian forces poorly for an extended fight in the area. They would need to defend a bridgehead on the western bank that would have to be resupplied over the river under fire.
Ukraine’s top military command said on Tuesday that up to three Russian battalions had launched a ground assault on Avdiivka, supported by tanks and armored vehicles.
A Russian military blogger who has closely tracked the war from the Russian perspective, Rybar, posted on Telegram that Russian forces had broken through Ukrainian defenses near villages outside Avdiivka in a maneuver seeking to surround the town. His claims could not be independently verified.
Mr. Bielieskov, the Ukrainian military analyst, said the Russians faced steep challenges in trying to capture Avdiivka because the city was very well defended. Ukrainians have used the grounds of a coking coal factory as a fortress, and in one location dug so many trenches and bunkers that the position gained the nickname “the anthill.”
“Avdiivka is a very important strong point in the Ukrainian system of defense,” Mr. Bielieskov said, noting that Russian forces had repeatedly tried to seize the town. But if it were captured, he said, the loss could compromise Ukraine’s positions nearby because the town is a linchpin of regional defenses. Two other cities, Pokrovsk and Kostiantynivka, rely on the defenses in Avdiivka
The Institute for the Study of War, a Washington-based think tank, said on Tuesday that a successful encirclement “would very likely require more forces than Russia has currently dedicated” to its offensive efforts there.
Avdiivka is a suburb of the city of Donetsk, and part of a line of small towns that forms an arc to the city’s west. They have been on a front line since a Russian military intervention in eastern Ukraine in 2014.
That positions in Avdiivka have held through eight years of the low-intensity war in eastern Ukraine, and a year and a half of full-scale assaults by the Russian army has made the town a symbol of Ukrainian resistance. Ukrainian forces have held out through airstrikes and continual artillery bombardment. The town, once home to about 30,000 people, is now mostly empty ruins.
