Ukraine says it has recaptured ground in Bakhmut, a rare advance after months of grinding Russian gains in the eastern city.
Deputy Defence Minister Hanna Malyar said Ukrainian forces advanced two kilometers (1.2 miles) in a week.
The claims signal a momentum shift in Bakhmut – but more widely, there is no clear evidence of the much-anticipated Ukrainian counter-offensive.
Russia has denied reports of Ukrainian gains, after claims from both sides.
“The individual declarations on Telegram about a ‘breakthrough’ on several points on the frontline do not correspond to reality,” Russia’s defence ministry said.
“The general situation in the special military operation zone is under control,” it added, using Russia’s term for the invasion.
However, in a updated statement on Friday morning the ministry claimed Russian troops had changed their position for strategic reasons.
It said units of the southern group of Russian forces had taken up a better defensive position in the Maloilinivka area, something which took into consideration “the favourable conditions of the Berkhivka reservoir”.
Maloilinivka and Berkhivka are both near Bakhmut.
Responding to the statement, the head of Russia’s Wagner mercenary group Yevgeny Prigozhin said what the Ministry of Defence was talking about “is unfortunately called ‘fleeing’ and not a ‘regrouping'”.
As the intense, bloody battle has worn on, Bakhmut has become symbolically important – though many experts question its tactical value.
In a post on Telegram, Ms Malyar said Bakhmut has become a target of “almost sacred” importance to Russia.
She accused the Kremlin of simultaneously claiming false victories on one hand, while also spreading lies about being short on weapons and ammunition.
Describing the “real situation” over the past week, Ms Malyar claimed Russia suffered significant troop losses, as Ukraine gained 2km without losing any positions.
Earlier Prigozhin accused regular Russian troops of abandoning positions in Bakhmut.
“The situation on the flanks is developing according to the worst predicted scenario,” he said.
And Russian military bloggers reported Ukrainian advances or troop movements in several areas.
The Institute for the Study of War also said Ukrainian forces had probably made gains of 2km in Bakhmut.
And the US-based think tank said the Russian defence ministry acknowledging “the Ukrainian counterattacks uncharacteristically quickly” – by denying them – indicated “increased panic”.
Away from Bakhmut, the exiled mayor of Melitopol reported a large explosion on Friday morning in the center of the city in south-eastern city, which has been occupied by Russia since the start of the war.
It’s not known what caused the blast, but the Ukrainian air force made 14 strikes on Russian forces and military equipment on Thursday, Ukraine’s armed forces said.
Alongside the air strikes, Ukraine said it destroyed nine Russian drones and carried out successful attacks on dozens of military targets – including artillery units, an ammunition warehouse and air defence equipment.
After months of stalemate, a Ukrainian counter-offensive – helped by newly-arrived Western weapons – has been openly discussed. But Ukraine’s president said on Thursday it was too early to start the attack.
“With [what we already have] we can go forward and, I think, be successful,” President Volodymyr Zelensky said in an interview.
“But we’d lose a lot of people. I think that’s unacceptable. So we need to wait. We still need a bit more time.”
But despite President Zelensky’s words, pro-Kremlin Russian war correspondent Sasha Kots claimed the counter-offensive had begun.
Ukrainian tanks were on the Kharkiv ring road heading towards the border with Russia, he said, quoting “trusted” sources. His claims could not be independently verified.
“There are low loaders in the columns carrying Western [tank] models among others,” Kots added.
“In other words,” he said, “Kiev [Kyiv] has decided to aggravate the situation along the northern front in parallel with the start of offensive actions on the flanks of Artyomovsk [the Russian name for Bakhmut].”
Another Russian war correspondent, Alexander Simonov, wrote on Telegram that Ukrainian forces had broken through near the village of Bohdanivka, close to Bakhmut, taking “several square kilometres” of ground.
Ukrainian military analyst Oleksandr Musivenko said Kyiv recognised that the anticipated counter-offensive might not necessarily defeat Russia “in all occupied areas”.
He told Ukrainian NV radio there was every possibility the war could continue into next year. “It all depends on how the battles develop. We can’t guarantee how the counteroffensive will develop,” he said.
An unnamed senior US military official told CNN that Ukrainian forces were preparing for a major counter-offensive by striking targets such as weapons depots, command centers and armour and artillery systems.
Ukraine’s spring 2022 advances in the southern and north-eastern parts of the country were also preceded by air attacks to “shape” the battlefield.
Russia’s defence ministry said it stopped several Ukrainian attacks throughout Thursday and said an ongoing battle near Malynivka, in eastern Donetsk, involved both air and artillery forces.