The fate of the Ukrainian city of Soledar was unclear on Wednesday, with Russian mercenary group Wagner claiming control of it while also saying "urban battles" were still being fought.
Both sides have said the battle for Soledar, known for its salt mines, has been intense and bloody. Its fall would mark a significant victory for Moscow's forces.
Soledar, in the Donetsk region, lies 15 kilometres (nine miles) from the city of Bakhmut, which Russia has been trying to seize for months.
Yevgeny Prigozhin, the head of Russia's controversial mercenary Wagner group, claimed in the early hours of Wednesday that his fighters seized control of the town.
"Wagner units have taken control of the whole territory of Soledar," Prigozhin alleged on social media.
But the the Kremlin-linked businessman added that "urban battles are being fought in the city centre".
He also said "the number of captives" will be announced Wednesday.
He posted a photograph of himself in military attire, surrounded by Wagner fighters, without saying where it was.
Russian state news agency RIA Novosti published another photograph of Prigozhin with armed fighters, saying it was taken in the salt mines of Soledar.
Prigozhin has said Soledar had been stormed "exclusively" by Wagner units.
The Russian army has not yet commented.
Ukraine said this week its fighters were holding out against intense assaults on the city.
"Even after suffering colossal losses, Russia is still maniacally trying to seize Soledar," Kyiv's defence ministry said late on Tuesday.
President Volodymyr Zelensky said there was a "difficult situation" in the Donetsk region in his daily night address on Tuesday. He praised the "bravery" of Ukrainian soldiers defending Soledar.
Earlier this week he said Soledar had been flattened by fighting: "Everything is completely destroyed."
The UK said Tuesday that Moscow's forces were "likely in control" of Soledar.
The potential fall of Soledar came as Russian strikes hit the major city of Kharkiv further north, just hours after a surprise visit by Germany's foreign minister Annalena Baerbock.
Kharkiv has faced heavy bombardment during the war, but the frontline has moved east since a Ukrainian counter-offensive last year retook territory from Russian forces.
Baerbock vowed further German support for Kyiv on her unannounced trip.
But her Ukrainian counterpart Dmytro Kuleba, who accompanied her, said Berlin's refusal to send Kyiv battle tanks was costing lives.
German Chancellor Olaf Scholz recently agreed to provide to Ukraine Marder infantry fighting vehicles long sought by Kyiv in its battle against Russia's offensive.
But Berlin has so far declined to supply Ukraine with more advanced Leopard battle tanks.
The "longer it takes to make the decision, the more people will die", Kuleba said.
Last week, France's Emmanuel Macron promised Zelensky that Paris would send French-made light tanks to Kyiv. This would make France the first Western country to deliver tanks to Ukraine.
The move has put pressure on Germany.
Baerbock stressed that Germany will keep supplying weapons "that Ukraine needs in order to free its citizens who are still suffering under the terror of Russian occupation".
Baerbock brought with her a "further help package" of power generators, 20 million euros ($21 million) for demining and 20 million euros as financial help for the Starlink project ensuring internet access in the country.
Several Western leaders have visited Ukraine since the Kremlin launched its offensive on February 24 last year, but none have travelled so far east as Baerbock.
Her visit was kept secret for security reasons and announced only as she made her way back to Berlin.
Putin ally stripped of citizenship
Zelensky on Tuesday also said he had revoked the citizenship of Viktor Medvedchuk, once seen as Russian leader Vladimir Putin's top ally in Kyiv.
Medvedchuk, a former Ukrainian lawmaker who was handed over to Russia in a prisoner exchange last September, was stripped of his citizenship along with three others, Zelensky said in his daily address.
The move was appropriate for those who "choose to serve not the people of Ukraine, but the murderers who came to Ukraine", Zelensky said.
Ukrainian tycoon Medvedchuk was captured in April last year by Ukraine's special services, after fleeing home arrest when Russia launched its offensive.
The super-rich powerbroker -- once dubbed the "dark prince" of Ukrainian politics -- was accused of high treason and attempting to steal natural resources from Russia-annexed Crimea and of handing Ukrainian military secrets to Moscow.