The key Ukrainian town of Avdiivka fell to a Russian advance as Moscow claimed "full control" despite some of Kyiv's troop presence at a vast Soviet-era coke plant.

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.

Ukraine said it had withdrawn its soldiers to save troops from being fully surrounded after months of fierce fighting. 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 mobilization and President Volodymyr Zelenskyy 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 Defense Ministry spokesman Igor Konashenkov said.

There was no public comment yet by Ukrainian authorities on this.

The Russian Defense Ministry said Russia had taken about 32 square kilometers (12 square miles) of territory in the advance amid heavy losses for Ukraine. It gave no figures for Russian losses, which Ukraine says are huge.

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 had a pre-war population of around 32,000 and is called Avdeyevka by Russians, 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.

Weapons shortages

U.S. President Joe Biden had warned that Avdiivka could fall to Russian forces because of ammunition shortages following months of Republican congressional opposition to a new U.S. military aid package for Kyiv.

A White House statement said Biden called Zelenskyy on Saturday to underscore the U.S. commitment to continue supporting Ukraine and reiterated the need for Congress to urgently pass the package.

The White House said the withdrawal had been forced upon Ukraine "by dwindling supplies as a result of congressional inaction," which had forced Ukrainian soldiers to ration ammunition and resulted in "Russia’s first notable gains in months."

Zelenskyy urged allies at a global security conference in Munich on Saturday to plug an "artificial" shortage of weapons and said stalled U.S. aid was imperative. He praised his troops for "exhausting" Russian forces in Avdiivka and suggested the withdrawal was partly caused by a lack of weapons.

"Now, (the military) will replenish, they will wait for the relevant weapons, of which there simply weren't enough, simply aren't enough," he said. "Russia has long-range weapons, while we simply don't have enough."

In a post on X, Zelenskyy expressed hope that the U.S. Congress would make a "wise decision."

Boost for Russia

Capturing Avdiivka will likely provide a morale boost for Russia ahead of Putin's bid for re-election next month, which he is almost certain to win.

It is also seen as another step toward securing Moscow's hold on the regional center of Donetsk, about 20 kilometers (12 miles) to the east, held by Russian and pro-Russian forces since 2014.

Neither Russia nor Ukraine have given details of their losses in the war or in the intense battle for Avdiivka. Western intelligence assessments say hundreds of thousands of men on both sides have been killed or wounded in the war.

Putin congratulated the Russian commander in charge of the assault on Avdiivka, Col. Gen. Andrei Mordvichev.

"Eternal glory to the heroes who fell in fulfilling the tasks of the special military operation!" Putin said in a telegram.

Ukrainian Defence Minister Rustem Umerov said Avdiivka showed the need for modern air defense systems to counter guided bombs and long-range weapons to destroy enemy formations. He said artillery shells were also needed.

Col. Gen. Oleksandr Syrskyi, who took command of the Ukrainian military in a major shake-up last week, said Ukrainian forces had moved back to more secure positions outside the town "to avoid encirclement and preserve the lives and health of servicemen."

Ukraine's 3rd Assault Brigade, which officials say was deployed to Avdiivka this week, said on Telegram that it had pulled back to prepared positions on the outskirts of Avdiivka and evened out the front line.

"At this time, the Russians are not slowing down their assault. We keep holding the line in the area of Avdiivka," it said.

Separately, Ukrainian forces repelled a Russian offensive on the southern front in the area of Zaporizhzhia, the Ukrainian military said Sunday.

There was no comment on that yet from the Russian side.