Russian forces close in on key Ukrainian city Pokrovsk

"As a result of prolonged clashes, two of our positions were destroyed, and one was lost. Actions are currently being taken to restore the position," said Nazar Voloshin, spokesman for the Ukrainian eastern front, on Ukrainian television.

The fall of Pokrovsk, an important logistical center for the Ukrainian army, would signify the largest military defeat for Kyiv in months. The city still has an operational mine, the only national coking coal supplier for Ukraine's once-massive steel industry.

The chief commander of Ukrainian forces, Oleksandr Syrskyi, said he visited the marine infantry unit near Pokrovsk and witnessed the conditions where the soldiers had to face an "enemy surpassing them mainly in numbers."

"I listened to information about the existing problems and gave appropriate orders. Ukrainian soldiers display extraordinary resilience and inflict significant losses on the enemy," Syrskyi wrote on Facebook.

"We must make unconventional decisions to increase the resilience of our defense and ensure more effective destruction of the occupiers. Russian occupiers are throwing all available forces into battle, trying to break through our troops' defense," he added.

For months, Pokrovsk has been an area of the fiercest fighting between Ukrainian and Russian forces. In October and November, Russian troops advanced towards this city at the fastest pace since the first months of the war.