Ukraine's military said it had withdrawn outnumbered troops from the southeastern part of the city of Avdiivka amid escalating battles, adding that the decision provided no strategic advantage for Russia.
Oleksandr Tarnavskyi, the commander of Ukraine's southeastern sector, said on Telegram Ukrainian units pulled back with minor losses.
"In a difficult battlefield situation, when only ruins and a pile of broken bricks remain from the fortification, our priority is to save the soldiers' lives," he said.
Tarnavskyi once again described the Avdiivka sector as "the hottest" on the entire front line of about 1,000 km (600 miles).
"The enemy launches massive bomb attacks day and night, and does not stop attacking simultaneously from several directions," he said.
It was not immediately possible for Reuters to confirm battleground reports.
Capturing the eastern city is seen as key to Moscow's aim of securing full control of the two provinces that make up the industrial Donbas region, and could hand Russian President Vladimir Putin, who recently underlined its significance, a battlefield victory to hold up to voters as he seeks re-election next month.
As troops were leaving the so-called Zenit fortified area in the city's southeast, President Volodymyr Zelenskiy said Kyiv's priority was to minimize losses, though the military was trying to defend strategic routes.
"Tactically, securing these positions does not give the enemy a strategic advantage and does not change the situation in the Avdiivka defence operation," Tarnavskyi said.
He added measures were taken to expand logistics routes, and munitions were delivered in increased volumes.
The Third Assault Brigade was recently sent to reinforce Ukraine's positions and Tarnavskyi said on Friday that "a planned strengthening of units" was taking place.
None of the Ukrainian troops was blocked by the enemy as of midday, he said, and defenders in other parts of the city were moving to prepared positions "if necessary".
Tarnavskyi noted that Russian troops suffered "enormous losses". The Third Assault Brigade echoed this comment.
One of the dangers, apart from being outnumbered and outgunned, was Russia's tactic of dropping guided bombs over the city. Maksym Zhorin, the brigade's deputy commander, said Russia was using between 60 and 80 of them per day.
"All buildings (and) structures are simply turned into a ditch after a strike by just one guided bomb," he wrote on Telegram.