The strategic city is considered to be "the gateway to Donetsk" - and its loss would be a huge blow to Ukraine's logistical abilities across the eastern front lines. Kiev has rejected Putin's claim to have the whole city surrounded and blockaded. "We are holding Pokrovsk," Ukraine's army chief Oleksandr Syrskii wrote on Facebook Saturday. "A comprehensive operation to destroy and dislodge enemy forces from Pokrovsk is ongoing."

Kiev's response involves the special forces units being sent to bolster potentially trapped Ukrainian forces - though this could soon prove too little, too-late. "Kyiv announced Saturday it had deployed special forces to the eastern city of Pokrovsk, where it is under pressure from an intense Russian assault involving thousands of troops," The Moscow Times wrote.

Recent days have seen Moscow and Kiev issue conflicting back-and-forth statements about the fighting in the city, with Russia's Ministry of Defense claiming that its troops had already defeated the Ukrainian special forces deployed there. It even later released videos purportedly showing two captured Ukrainian soldiers.

Gen. Syrskii has admitted that Ukrainian forces are facing their "hardest" time there currently. But he's still rejected Moscow's narrative of total battlefield encirclement of the city.

"The main burden lies on the shoulders of the units of the Armed Forces of Ukraine, particularly UAV [unmanned aerial vehicle] operators and assault units," Syrskii has said.

Russian officials over much of the past year of fighting there have consistently articulated that seizing Pokrovsk and the nearby city of Kostiantynivka would allow Moscow to advance north toward the last major Ukrainian strongholds in Donetsk - Kramatorsk and Sloviansk.

For the majority of the war Pokrovsk has acted as the logistical hub and rear operations base for Ukraine's eastern defensive lines. It sits astride both a key railroad juncture and the highway to Ukraine's fourth-largest metro, Dnipro. 

The loss of the primary rail lines and highway routes in and out of Pokrovsk would cut resources to Ukrainian units across the Donbas and possibly force them to retreat before running out of supplies. This would mean an immediate and sweeping Russian advance all along the eastern lines.