The fate of a devastated salt-mining town in eastern Ukraine hangs in the balance in one of the bloodiest ground battles of Russia’s invasion, as Ukraine’s unflagging resistance and other challenges prompt Moscow to shake up its military leadership again.

Russian forces using jets, mortars and rockets bombarded Soledar in what a Ukrainian military officer said was an unrelenting assault.

Soledar’s fall, while unlikely to provide a turning point in the nearly 11-month war, would be a prize for a Kremlin starved of good news from the battlefield in recent months. It would also offer Russian troops a springboard to conquer other areas of Donetsk province that remain under Ukrainian control, such as the nearby strategic city of Bakhmut.

Donetsk and neighbouring Luhansk province, which together make up the Donbas region bordering Russia, were Moscow’s main stated territorial targets in invading Ukraine, but the fighting has stood mostly at a stalemate.

In an apparent recognition of battlefield setbacks, Russia’s Defence Ministry announced the demotion of the head of Russian forces in Ukraine after only three months on the job. The chief of the military’s General Staff, General Valery Gerasimov, was named to replace Generla Sergei Surovikin, who was demoted to deputy, along with two other generals.

During his short time overseeing the troops in Ukraine, Surovikin was credited with strengthening coordination and reinforcing control. But he also announced a withdrawal in November from Kherson, one of the biggest and most important cities Russian forces had captured during the conflict. His demotion signalled that Russian President Vladimir Putin wasn’t fully satisfied with his performance.

The Defence Ministry said expanded military tasks and the need for “closer interaction between branches of the military as well as increasing the quality of supplies and the efficiency of directing groups of forces” prompted the leadership changes.

On the battlefield, a Ukrainian officer, near Soledar, told The Associated Press the pattern is that first the Russians send one or two waves of soldiers, many from the private Russian military contractor Wagner Group, who take heavy casualties as they probe the Ukrainian defences.

When Ukrainian troops have taken casualties and are exhausted, the Russians send a fresh wave of highly-trained soldiers, paratroopers or special forces, said the Ukrainian officer, who insisted on anonymity for security reasons.

Ukrainian Deputy Defence Minister Hanna Malyar and the spokesman for Ukraine’s Eastern Group of Forces, Serhiy Cherevaty, denied Russian claims Soledar had fallen, but Malyar acknowledged heavy fighting.

Late Tuesday (Wednesday NZ time), Yevgeny Prigozhin, the Wagner Group’s owner, claimed on his Russian social media platform that his soldiers had seized control of Soledar, though he also said fighting continued in a “cauldron” in the city’s centre.

The AP was unable to verify that claim.

Russian forces had achieved “positive dynamics in advancing” in Soledar, Kremlin spokesman Dmitry Peskov said on Wednesday, stopping short of declaring its capture.

“Let’s not rush, and wait for official statements,” he said.

Soledar, known for salt mining and processing, has little intrinsic value but it lies at a strategic point 10km north of the city of Bakhmut, which Russian forces want to surround.

Taking Bakhmut would disrupt Ukraine’s supply lines and open a route for the Russians to press toward Kramatorsk and Sloviansk, key Ukrainian strongholds in Donetsk province.

Soledar’s fall would make “holding Bakhmut much more precarious for Ukraine”, Michael Kofman, the director of Russia Studies at the CAN nonprofit research organisation in Arlington, Virginia, said.

The war of attrition, with heavy casualties, may make a Russian victory as deadly as a defeat.

“I don’t think the outcome at Bakhmut is that significant compared to what it costs Russia to achieve it,” Kofman said in a tweet.

The Wagner Group, which now reportedly includes a large contingent of convicts recruited in Russian prisons, has spearheaded the attack on Soledar and Bakhmut.

Western intelligence has estimated the Wagner Group constitutes up to a quarter of all Russian combatants in Ukraine.

A success in Soledar and Bakhmut would help Prigozhin, who has openly criticised Russia’s military leadership, increase his clout at the Kremlin.

Russian troops have struggled to gain control over Donetsk, Luhansk and two other Ukrainian provinces the Kremlin illegally annexed in September. Russia annexed the Crimean Peninsula in 2014. After Ukrainian forces recaptured the southern city of Kherson in November, the battle heated up around Bakhmut.

Putin identified the Donbas region as a focus from the war’s outset, and Moscow-backed separatists have fought there since 2014. Russia captured almost all of Luhansk during the summer. Donetsk escaped the same fate, and the Russian military subsequently poured manpower and resources around Bakhmut.

The Institute for the Study of War said Russian forces were up against “concerted Ukrainian resistance” around Bakhmut.

“The reality of block-by-block control of terrain in Soledar is obfuscated by the dynamic nature of urban combat ... and Russian forces have largely struggled to make significant tactical gains in the Soledar area for months,” the Washington-based think tank said.

An exceptional feature of the fighting near Bakhmut is that some has taken place around entrances to disused salt mine tunnels, which run for some 200km, according to Western intelligence reports.

On a different front, Ukrainian President Volodymr Zelenskyy on Wednesday visited the western city of Lviv for a high-level meeting on the security situation near Ukraine’s border with Russian ally Belarus.

A Ukrainian army Grad multiple rocket launcher fires rockets at Russian positions in the frontline near Soledar, Donetsk region, Ukraine, on Wednesday. Photo / AP

Russia has stationed more than 10,000 of its soldiers in Belarus and conducts regular military drills in the country, which shares a roughly 1000km border with Ukraine. The Kremlin used Belarus as a staging ground to send troops and missiles into Ukraine when Russia invaded February 24.

Concerns have risen that Moscow might pressure Belarus into opening up a new front in Ukraine’s west, possibly to target supply routes for Western weapons and other overseas aid that have helped Kyiv’s forces sustain a defence and launch a counteroffensive.

Zelenskyy said there were no immediate worries about Minsk joining the war, but added: “We must be ready.”

Meanwhile, Putin claimed on Wednesday that Russia had successfully resisted Western pressure, especially sanctions, over its invasion of Ukraine and vowed that his country has enough resources to beef up its military while continuing social programmes and meeting other development targets.

“Nothing of what our enemies forecast has happened,” Putin said in a video call with his Cabinet.

“We will strengthen our defence capability and will undoubtedly solve all issues related to supplies to military units involved in the special military operation,” he said, using the Kremlin’s euphemism for the war.

Reports have circulated that Russia is struggling to produce enough weapons, equipment and clothing for its troops battling in Ukraine.

In other developments:

• Polish President Andrzej Duda said his country is willing to send German-made Leopard tanks to help Ukraine as part of a larger international coalition of tank aid. Duda spoke after he and Lithuanian President Gitanas Nausėda met in Lviv with Zelenskyy, who said Ukraine needs tanks to win the war. In Britain, another staunch Ukraine ally, the spokesman for Prime Minister Rishi Sunak said no final decision has been made on whether to send tanks. The UK has been considering whether to provide Challenger 2 battle tanks.
• The Russian and Ukrainian human rights commissioners agreed to swap more than 40 military prisoners, Turkey’s state-run Anadolu Agency quoted the Russian official as saying. The two warring parties have exchanged prisoners multiple times, in one of the few areas of cooperation. Turkish President Recep Tayyip Erdoğan said his country has proposed establishing a corridor to bring the wounded to Turkey for treatment. “We can ensure they receive medical treatment and send them back,” Erdoğan said. “This is our humanitarian duty, our duty of conscience.” - Andrew Meldrum, AP