The Russian-installed governor of Ukraine's Donetsk region said on Wednesday that units of the Wagner contract militia were advancing in the town of Bakhmut, with fighting taking place in previously Ukrainian-held neighbourhoods.
Reuters could not independently confirm the battlefield claim by Denis Pushilin, the Russian-imposed head of the region, whose annexation was claimed by Moscow last September.
"Units, in particular Wagner, are advancing in Artyomovsk itself," TASS news agency quoted him as saying, using the Russian name for the town.
"Fighting is already taking place in the outskirts and in neighbourhoods that until very recently were held by the enemy," he said.
The area around Bakhmut has seen some of the most brutal fighting of the 11-month war, so its fate has high symbolic importance for both Russia and Ukraine, even though Western military analysts say the town, which had a pre-war population of around 70,000, has little strategic significance.
Russia said earlier this month it had captured Soledar, to the northeast, and Klishchiivka to the south, in advance for which Yevgeny Prigozhin's Wagner group claimed credit.
RIA news agency quoted Pushilin as saying that taking Soledar had made it possible to block Ukrainian supply routes and control some areas from which Ukrainian forces had been launching "retaliatory action".