Russia has said it has taken full control of the eastern Ukrainian city of Avdiivka, its biggest gain since capturing Bakhmut last May, after a retreat by Ukrainian troops. Ukrainian forces had withdrawn from the city in the industrial Donbas region to avoid encirclement, the army chief, Oleksandr Syrskyi, said on Saturday, adding that he had acted to “preserve the lives and health of servicemen”, stabilise the situation and move troops to more favourable defence lines. Some Ukrainian troops were still holed up in a vast Soviet-era coke plant, one of Europe’s biggest, Russia said, describing the retreat as rushed and chaotic. Ukraine’s military said there had been casualties in the retreat but that the situation had stabilised. The capture of Avdiivka gives Russia full control of the area surrounding Donetsk, a large Ukrainian city that was seized by Russian proxy forces in 2014, and comes as the second anniversary of its full-scale invasion of Ukraine nears. The Ukrainian army had struggled on the frontline around Avdiivka in recent months during one of the most intense battles of the war, which left the city almost destroyed and caused nearly all of the more than 30,000 prewar population to leave. The US president, Joe Biden, had warned that the city might fall to Russia due to weapons shortages exacerbated by months of Republican congressional opposition to a new US funding package for the Ukrainian military. The Russian president, Vladimir Putin, congratulated Russian soldiers on “the important victory”, the Kremlin said in a statement on its website on Sunday. Russia’s defence ministry spokesperson, Maj Gen Igor Konashenkov, said measures were 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 state television showed blue and yellow Ukrainian flags being taken down in Avdiivka and Russia’s white, blue and red tricolour raised, including over the coke plant. After the failure of Ukraine to pierce Russian lines last year, Moscow has been trying to grind down Ukrainian forces just as Kyiv weighs up a major new mobilisation and Volodymyr Zelenskiy has appointed a new commander to run the war. At a security conference in Munich on Saturday, the Ukrainian president urged western allies to help his country defeat “the monster”, referring to Putin. Separately, Ukrainian forces repelled a Russian offensive on the southern front in the area of Zaporizhzhia, the Ukrainian military said on Sunday. Avdiivka 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 recaptured by Ukrainian troops who built extensive fortifications. On Wednesday 21 February at 7pm GMT Guardian Live will be holding an online event about the Russia-Ukraine war, with panellists including Luke Harding, Charlotte Higgins and novelist Andrey Kurkov. Book tickets here.