Ukraine's military leadership has replaced the commander overseeing the defense of the eastern Donetsk region, where Russian forces are advancing rapidly, a military official quoted by "Reuters" said.
General Oleksandr Tarnavsky, 54, was appointed to lead the Donetsk operational-tactical group, replacing General Oleksandr Lutsenko, a representative of the General Staff told Reuters.
Lutsenko was criticized by Ukrainian military bloggers and some lawmakers for failing to stop the relentless push by Russian troops towards the strategic Ukrainian city Pokrovsk.
The fighting around Pokrovsk, a key logistics hub for Ukrainian military and civilians in eastern Donetsk region, comes at a critical moment in the war.
Ukraine is on the back foot on the battlefield as Russian troops advance at their fastest pace since the early days of Moscow's invasion in February 2022.
Last month, President Volodymyr Zelensky replaced several other generals, saying changes were needed.
Kiev is also trying to build ties with US President-elect Donald Trump, whose promise of a quick end to the war has raised concerns in Ukraine that it could be largely on Moscow's terms.
The Ukrainian military command of the Khortytsia group of forces said on Saturday that Russian troops had destroyed several Ukrainian positions in villages around Pokrovsk, improving their tactical positions after "exhausting battles" and forcing Kiev forces to retreat.
In its daily report, the Ukrainian military reported a total of 62 clashes near Pokrovsk over the past 24 hours.
Ukrainian officials said about 11,000 people still remained in Pokrovsk, which has been under constant shelling for months and where all critical infrastructure - electricity, water and gas supplies - has been destroyed.
Pokrovsk is located at the intersection of several important roads and railways and is only about 20 kilometers from the administrative border of Donetsk Oblast. Moscow has been trying to reach this line since the beginning of the invasion, as its forces seek to capture the entire Donetsk and Luhansk regions.
For Kiev, the loss of Pokrovsk would potentially mean the war moving closer to central Ukraine and its better-defended rear.