Russia on Sunday said it had full control of the Ukrainian town of Avdiivka after Ukraine withdrew.
Moscow said, however, that some Ukrainian troops were still holed up in a vast Soviet-era coke plant after one of the most intense battles of the war.
The fall of Avdiivka is Russia's biggest gain since capturing the city of Bakhmut in May 2023, and comes almost two years to the day since president Vladimir Putin triggered a full-scale war by ordering the invasion of Ukraine.
Russia's defence ministry said its troops had advanced 8.6 km (5.3 miles) in that part of the 1,000-km (620-mile) front line, and that Russian troops were pressing forward after a deadly urban battle that has left the town an almost completely depopulated wreck.
Ukraine said it had withdrawn its soldiers to save troops from being fully surrounded after months of fierce fighting. Mr Putin hailed the fall of Avdiivka as an important victory and congratulated Russian troops.
After the failure of Ukraine to pierce Russian lines last year, Moscow has been trying to grind down Ukrainian forces just as Kyiv ponders a major new mobilisation and president Volodymyr Zelensky appoints a new commander to run the war.
"The head of state congratulated Russian soldiers on this success, an important victory," the Kremlin said in a statement on its website.
But Russia said some Ukrainian forces were still holed up at the Soviet-era coke plant, once one of Europe's biggest, in Avdiivka, which is key to Russia's aim of securing full control of the industrial Donbas region.
"Measures are being taken to completely clear the town of militants and to block Ukrainian units that have left the town and are entrenched at the Avdiivka Coke and Chemical Plant," Russian defence ministry spokesman Igor Konashenkov said.
There was no public comment yet by Ukrainian authorities on this. Russian state television showed blue and yellow Ukrainian flags being taken down in Avdiivka and Russia's white, blue and red tricolour flag raised, including over the coke plant.
Russia cast the Ukrainian withdrawal as rushed and chaotic, with some soldiers and weapons left behind. The Ukrainian military said there had been casualties but that the situation had stabilised somewhat after the retreat.
Putin sent tens of thousands of troops into Ukraine in February 2022, triggering the full-scale war after eight years of conflict in eastern Ukraine between Ukrainian forces on the one side and pro-Russian Ukrainians and Russian proxies on the other.
Avdiivka, which is called Avdeyevka by Russians, has endured a decade of conflict. It holds particular symbolism for Russia as it was briefly taken in 2014 by Moscow-backed separatists who seized a swathe of eastern Ukraine but was then recaptured by Ukrainian troops who built extensive fortifications.
