The town of Pokrovsk plays a crucial role as a logistics hub used by Ukrainian forces in the eastern region of Donbas, BBC reports. It is home to a key railway station, and it is located at the intersection of several important roads.
Russian forces have for months sought to capture the town, but their advance has quickened this month and they are now thought to be less than 10km (6 miles) away.
Before the war, Pokrovrsk was home to some 69,000 residents, with many of them employed in coal mining, metallurgy and machine-building.
Thousands left in recent months as the Russians advanced, but now families with children have been ordered to evacuate too. Civilians had only a week or two to get out, Serhiy Dobriak warned last Monday.
Ukraine had hoped that by seizing territory in Russia's Kursk region it would be able to divert Russian troops away from their eastern advance, but that has not happened. If anything the Russian offensive on Pokrovsk, and Toretsk further to the north east, has intensified.
"Pokrovsk is a very important hub, a centre of defence. If we lose Pokrovsk, the entire front line will crumble," military expert Mykhaylo Zhyrokhov warned.
Ukraine relies on the town's rail and road infrastructure to provide supplies and reinforcements to its troops on the eastern front line, as well as to evacuate the wounded.
Losing Pokrovsk to Russian forces would mean these vital military tasks would become far more complicated.
It would also increase the risk to other strategically important towns, such as Chasiv Yar, which sits atop commanding heights giving control over the wider area.
