Both Ukraine and Russia reported high casualties in Ukraine's Donbas region, the focus of Moscow's slow, long-running advance into its neighbour's territory.
Much of the fighting in the east has centred on Bakhmut, largely destroyed in months of attacks and shelling by Russia during the year-old conflict.
Russia's defence ministry said its forces were conducting further military operations in Donetsk region which, together with adjacent Luhansk region, makes up Donbas.
The ministry said Russian forces had killed more than 220Ukrainian service members over the past 24 hours.
"In the Donetsk direction... more than 220 Ukrainian servicemen, an infantry fighting vehicle, three armoured fighting vehicles, seven vehicles, as well as a D-30 howitzer were destroyed during the day," the ministry said.
Moscow says capturing Bakhmut would punch a hole in Ukrainian defences and be a step toward seizing all of the Donbas industrial region.
Russian forces suffered more than 1,100 dead in less than a week of battles near the eastern Ukrainian city of Bakhmut, Ukrainian President Volodymyr Zelensky has said.
"In less than a week, starting from 6 March, we managed to kill more than 1,100 enemy soldiers in the Bakhmut sector alone, Russia's irreversible loss, right there, near Bakhmut," he said in his nightly video address.
He said Russian forces had also sustained 1,500 "sanitary losses" - soldiers wounded badly enough to keep them out of further action. Dozens of pieces of enemy equipment were destroyed as were more than 10 Russian ammunition depots.
Reuters could not independently verify the accounts.
Some military experts have questioned the sense of continuing to hold the city, but the commander of Ukraine's ground forces, Oleksandr Syrsky, said that it helped win time in preparation for the coming counteroffensive.
"The real heroes now are the defenders who are holding the eastern front on their shoulders, and inflicting the heaviest possible losses, sparing neither themselves nor the enemy," Mr Syrsky was quoted as saying in a statement.
"It is necessary to buy time to build reserves and launch a counteroffensive, which is not far off."
In a video released yesterday, Yevgeny Prigozhin, chief of Russian mercenary group Wagner, said that his forces were close to the administrative centre of the city.
Standing on the rooftop of a high-rise building in what is said to be Bakhmut, Mr Prigozhin is seen pointing towards a building in the distance.
"This is the building of the town administration, this is the centre of the town," he said, clad in full military gear.
"It is one kilometre and two hundred metres away."
Speaking as artillery boomed in the background, Mr Prigozhin said the most important thing now was to receive more ammunition from the army and "move forward".
Wagner has been spearheading offensives against cities in eastern Ukraine including Bakhmut. Both sides have suffered heavy losses.
The Ukrainian defence ministry yesterday reported that its forces had repelled "more than 100 enemy attacks" over the last day along the eastern front.
'A killing zone'
In an interview with the French newspaper Journal du Dimanche, Ukrainian Deputy Prime Minister Olga Stefanishyna underscored the human cost of Russia's assault on Bakhmut.
"Thousands of Russian soldiers died at a considerable rate in this battle," she said. "The human mass of its infantry is a formidable weapon, it seems inexhaustible in volume and in time."
But even if it did capture the "small town", she added, "it will not impact the strategic corridors we still control in the region".
British military intelligence said that the Bakhmutka River in the centre of the city now marked the front line.
"Ukrainian forces hold the west of the town and have demolished key bridges over the river, which runs north-south through a strip of open ground 200 metres-800 metres wide," the British defence ministry said.
"This area has become a killing zone, likely making it highly challenging for Wagner forces attempting to continue their frontal assault westwards."
Mr Prigozhin, an ally of President Vladimir Putin, has been entangled in a power struggle with the defence ministry.
He has several times claimed battlefield victories ahead of Russia's army, criticised the country's top brass and accused the military of not sharing ammunition with Wagner forces.
In an interview published today, he had ambitions to turn his private military company into an "army with an ideology" that would fight for justice in Russia.
"After the capture of Artyomovsk, we will begin to reboot," Mr Prigozhin said in a clip posted on Telegram.
"In particular, we will start recruiting new people from the regions.
"The Wagner private military group must turn from just a private, the best, army in the world which is capable of defending the state, into an army with an ideology. And that ideology is the struggle for justice".
Yesterday, he said he was ready to ask Russia's top commanders for forgiveness but at the same time appeared to mock Russian Defence Minister Sergei Shoigu and Chief of the General Staff Valery Gerasimov.
He said they were "outstanding military commanders" and added that Russia's greatest military leaders including Georgy Zhukov and Alexander Suvorov "could have learnt" from them.
"I absolutely -- totally -- support all their initiatives," Mr Prigozhin added.
