Fighting between Russian and Ukrainian forces has reached the outskirts of Severodonetsk, a significant eastern Ukraine city, according to the regional governor, who described the battle as “extremely difficult.”

“Russian troops have moved far enough that they may already fire mortars” on the city, according to Lugansk governor Sergiy Gaiday, who added that “there was already fighting on the outskirts yesterday.”

Moscow’s army has plotted a slow but steady course deeper into Ukraine’s eastern Donbas region since withdrawing forces from central and northern regions to consolidate military efforts in the east.

Severodonetsk, with a pre-war population of around 100,000 people, has been under relentless Russian shelling for weeks and is among key urban hubs in the industrial Donbas region on Russia’s list of military goals.

“The coming week will be decisive,” Gaiday said, adding that he believes Russia’s goal is to “capture the Lugansk region no matter what cost”.

Severodonetsk is “operationally besieged” by rebel troops and Russian forces, according to a representative of Moscow-backed separatist militants who has controlled parts of Lugansk since 2014.

“It’s only possible to exit from Severodonetsk via one bridge, which is also under the control of our firepower,” the separatist official told Russia’s Interfax news agency.