KRAMATORSK, Ukraine — Ukrainian forces on Sunday hunted Russian stragglers in the key city of Lyman, which was taken back from Russia after its demoralized troops, according to a major Russian newspaper, fled with “empty eyes,” and despite Moscow’s baseless claim it had annexed the region surrounding the city.
Two days after President Vladimir V. Putin held a grandiose ceremony to commemorate the incorporation of four Ukrainian territories into Russia, the debacle in the city — Lyman, a strategic railway hub in the eastern region of Donbas — ratcheted up pressure on a Russian leadership already facing withering criticism at home for its handling of the war and its conscription of up to 300,000 men into military service.
Russia’s retreat from Lyman, which sits on a riverbank that has served as a natural division between the Russian and Ukrainian front lines, came after weeks of fierce fighting.
In an unusually candid article published Sunday, the prominent Russian newspaper Komsomolskaya Pravda reported that in the last few days of their occupation, Russian forces in Lyman had been plagued by desertion, poor planning and the delayed arrival of reserves.
“The risk of encirclement or shameful imprisonment became too great, and the Russian command made a decision to fall back,” a war correspondent traveling with the fleeing Russian forces wrote, adding that dispirited soldiers with “empty eyes” had barely escaped Lyman with their lives.
The retreat is a significant blow to Russian forces that could further undermine the Kremlin’s position in Donbas, a mineral-rich and fertile part of eastern Ukraine that has been central to Mr. Putin’s war aims.
Mr. Putin’s office made no public comment about the loss of Lyman, even as pro-war commentators and two of his closest allies sharply criticized the Defense Ministry for retreating from the city. Seemingly unfazed by its military setbacks, Moscow pressed ahead with its annexation effort on Sunday, as the country’s rubber-stamp Constitutional Court formally accepted Mr. Putin’s decision to claim the four Ukrainian regions as part of Russia.
But President Volodymyr Zelensky of Ukraine quickly sought to capitalize politically on the retreat, saying it showed that Moscow’s attempt to illegally annex a sizable part of the country was an “absolute farce” and that “now a Ukrainian flag is” in Donbas. But the Ukrainian recoveries in areas Russia now claims have come as Mr. Putin has increasingly hinted at turning to nuclear options in the conflict, alarming American officials.
On Friday, after Russian-appointed officials held discredited referendums in the four partly occupied areas of Ukraine, Mr. Putin announced that the territory, including Lyman, would be absorbed into Russia and that its people would be Russian citizens “forever.”
Mr. Putin claimed the provinces’ residents had voted overwhelmingly to join the Russian Federation, but Ukraine and its Western allies dismissed the referendums as shams, as most of the citizens had fled the region and many of those left behind had cast ballots at gunpoint.
Despite the Russian leader’s claims and bluster at the ceremony on Friday in a grand Kremlin hall — he denounced Washington for “Satanism” — Russian troops retreated from Lyman barely a day later.
Initially, Ukrainian commanders thought they would retake Lyman quickly, with forces nearly completely encircling the city. But Russia’s military sent reinforcements. Fierce fighting ensued in dense forests and along the banks of the Siversky Donets River as Ukraine cut off the roads used to move troops and ammunition into the city.
“In Lyman and around it, there were significantly strong forces,” Col. Sergei Cherevaty, a spokesman for Ukrainian troops fighting in the east, said in an interview.
Russian soldiers retreated chaotically, breaking from their units and escaping in smaller groups into the surrounding forests, Colonel Cherevaty said, and many were killed or captured. About 2,000 to 3,000 Russian soldiers were in Lyman as Ukrainian forces arrived on the outskirts of the city on Friday, he said.
As Ukrainian soldiers and police officers fanned out across Lyman to search for Russian stragglers, it was unclear on Sunday how many had fallen into Ukrainian hands.
Mr. Zelensky said the city had been fully cleared by Sunday afternoon, as Ukrainian forces conducted patrols and delivered aid to residents who had survived months of Russian occupation and weeks of combat.
Artillery strikes have damaged much of Lyman. The city lies largely in ruins, without electricity, water or regular food supplies, according to Stanislav Zagrusky, the police chief of the Kramatorsk District, which includes Lyman.
Mr. Zagrusky said in an interview that the resumption of Ukrainian police patrols late on Saturday — hours after the Ukrainian Army declared the city liberated and Russia’s military conceded that it had retreated — underlined the absurdity of the Kremlin’s claim of sovereignty over the four Ukrainian territories.
“We absolutely don’t care what they say, what decrees they issue, what announcements they make,” he said of the Kremlin authorities, deploring the conditions in which Russian troops had left residents of Lyman during the occupation: “They did absolutely nothing for the people all this time.”
“They didn’t try to restore electricity or water, and people lived without regular food supplies,” he went on, adding that many residents needed medical care.
Mr. Zagrusky said that while the Ukrainian military took prisoners after the battle, police officers had made no arrests of Russian stragglers as of midday Sunday. His officers found that Russians had hastily abandoned a police station, leaving it littered with garbage.
The police said about 5,000 people remained in the city, which had a prewar population of 20,000.
As Ukrainian forces gained full control of Lyman, commanders turned their attention to the next steps in a punishing offensive that has left Russian troops in the eastern Donbas region in an increasingly perilous position.
From Lyman, Ukraine could push farther east to try to expel Russian troops from towns and villages they had seized over the summer, though colder temperatures could slow the fighting and Russian lines are expected to be reinforced by newly drafted troops.
Military analysts also warn that Ukrainian forces, if they push too far, could become overstretched and unable to defend newly reclaimed territory from Russian counterattacks.
None of the four illegally annexed regions are fully under Russian control. Ukrainian gains in the east and south have left the Kremlin’s forces with diminishing options for taking additional territory.
In the south, Ukrainian forces are engaged in a fierce counteroffensive in the Kherson region, which Russia seized in the first weeks of the war. Unlike in the northeast, there has been little movement in either direction, though odds increasingly appear to be stacked against Russian forces, the bulk of which have been cut off from their supply lines by successful Ukrainian attacks on key bridges spanning the vast Dnipro River.
On the other side of the Dnipro, Russian forces trying to push north in the Zaporizhzhia region, which Mr. Putin also claimed to have annexed, have been held at a standstill for months by strong Ukrainian defensive lines.
For now, Russian troops fleeing Lyman appear to be moving to reinforce their lines 25 miles to the south around the city of Bakhmut. That appears to be the only area along the extensive eastern front line where Russian forces are on the offensive, led primarily by members of the Wagner Group, a private military contractor, whose fighters have been pummeling Ukrainian forces for months.
“It’s very difficult because they have been hammering for several months with artillery and are constantly attacking with tanks and infantry,” Colonel Cherevaty said. “Holding them is difficult, but they’re managing.”
Andrew E. Kramer reported from Kramatorsk, Ukraine, Michael Schwirtz from Kyiv, Ukraine, and Norimitsu Onishi from Montreal.