Drone footage provides a view of Pokrovsk with the Ukrainian city at the centre of an attritional battle which may also define control of the Donetsk region.

Fighting in the city has reached a key stage, with Russian and Ukrainian forces so enmeshed that in some cases they’re vying for control of the same residential building, soldiers and analysts told The Associated Press.

Far from the battlefield, Pokrovsk is also critical to a diplomatic struggle, as both Kyiv and Moscow attempt to convince U.S. President Donald Trump that they have the upper hand in the fighting and the other side is weaker.

Russia says its forces have surrounded Pokrovsk and thwarted a Ukrainian operation to reopen logistics lines into the city.

Ukraine denies there’s a blockade, describing the fighting as ongoing, with its forces inflicting heavy Russian losses.

Russian forces entered Pokrovsk last month, taking advantage of gaps in Ukrainian defenses to slip through the lines, and appear poised to seize all of it in the coming weeks or months, experts say.

Ukrainian commanders on the ground admit the outlook is bleak.

Russia’s recent success in Pokrovsk is the result of more than a year of grinding battles in which its forces advanced 39 kilometers (24 miles), according to calculations by the U.S.-based Institute for the Study of War.

Neither Russia nor Ukraine disclose their casualty figures comprehensively, but analysts say that thousands of soldiers have been killed.

The operation progressed, meter by meter, until last month when Russian assault groups overcame worn-down Ukrainian defenses.

In response, Ukraine deployed its elite units, launching a special operation last week to counter potential advances. Commanders warn that the intense street-to-street fighting is reaching a critical point.

Pokrovsk sits along the eastern front line, part of what has been dubbed the “fortress belt” of Donetsk, a line of heavily fortified cities crucial to Ukraine’s defense of the region, including Kramatorsk, Sloviansk and Druzhkivka.

Pokrovsk, which had a prewar population of 60,000, once served as a crucial logistics hub for Ukrainian forces.

However, Russia used its artillery to establish an advantage over key routes, denying Ukrainian forces the ability to move freely, conduct evacuations and ferry in supplies.