KYIV, Ukraine (AFP)— A top Ukrainian commander on Thursday threatened an impending counterattack against Russian forces in the frontline town of Bakhmut as President Volodymyr Zelensky visited Kherson, still partially controlled by Russia.

Oleksandr Syrsky, commander of Ukraine's ground forces, said Russian troops were "exhausted" near Bakhmut, the scene of the longest and bloodiest battle since the Russian invasion last year.

Bakhmut -- an eastern town which once had an estimated population of around 70,000 people -- has virtually emptied of civilians over months of fierce fighting between Russian and Ukrainian forces.

"The aggressor has not given up hope of taking Bakhmut at all costs despite losses in manpower and equipment," said Syrsky.

"Sparing nothing, they are losing significant strength and becoming exhausted.

"Very soon we will take advantage of this opportunity, like we did near Kyiv, Kharkiv, Balakliya and Kupiansk," he added, referring to successful Ukrainian counteroffensives last year.

Kyiv considers Bakhmut key to holding back Russian forces along the entire eastern front.

Both sides have invested heavily in the fight, even though analysts say the city has little strategic value.

The head of Russia's Wagner mercenary group said this week that his forces were in control of around 70 percent of the city. A Russian aide in the wider Donetsk region has said the city was "practically surrounded".

Zelensky on Wednesday recognised troops had a "difficult" task as he visited the eastern front near Bakhmut.

On Thursday, he said he was on a "working trip to Kherson region" -- the southern region still partly controlled by the Russians, who are dug in on the eastern bank of the Dnipro river and routinely shell Kherson city, killing civilians.

Ukrainian forces recaptured Kherson city, the administrative centre of the southern region, last November following a strategic withdrawal of Russian forces.

Zelensky said his visit included one village where "houses and civilian infrastructural facilities were damaged" as a result of Russia's invasion.

He said local authorities were restoring essential services like electricity and water in the village and rebuilding a medical centre.

"People are returning," he said in the post on social media Thursday.

"I talked to the locals about their problems and needs," he added.

Kherson, a gateway to the Black Sea and the Sea of Azov, was captured easily and early by Russian forces in the early days of their February 2022 invasion.

Russian President Vladimir Putin claimed to have annexed Kherson and three other regions in Ukraine last September, despite not having full military control over any of them.

Zelensky, in a separate post, said he held a coordination meeting with officials and discussed de-mining and reconstruction in recaptured territory.

The head of Kherson's regional military administration, Oleksandr Prokudin, said Russian forces had killed one person and wounded two others over the last 24 hours.