Russia forces on Tuesday stepped up their weeks-long drive to encircle the eastern Ukrainian city of Bakhmut where the commander of Ukraine’s ground forces described the situation as “extremely tense”.

Russian forces are trying to cut the Ukrainian defenders’ supply lines to the city, scene of some of the war’s bloodiest battles, and force them to surrender or withdraw.

That would give Russia its first major prize in more than half a year and open the way to the capture of the last remaining urban centres in the Donetsk region, which Moscow claims to have annexed along with three other Ukrainian regions.

“Despite significant losses, the enemy threw in the most prepared assault units of Wagner, who are trying to break through the defences of our troops and surround the city,” Ukraine’s Colonel General Oleksandr Syrskyi was quoted as saying on a military messaging platform.

Russia’s RIA news agency released a video clip which it said showed Russian Su-25 fighter jets roaring over Bakhmut.

“We are glad they are ours,” says a man in the clip identified as a Wagner fighter, adding the jets helped them “psychologically”.

Ukrainian President Volodymyr Zelensky, who has described Bakhmut as “our fortress” that must be defended to the last, said in his nightly radio address that Russian forces “are constantly destroying everything that can be used to protect our positions for fortification and defence”.

Ukraine’s military said Russia was also shelling settlements around Bakhmut, which had a pre-war population of around 70,000 but now lies in ruins after months of intense trench warfare.