According to a communique, Anatoliy Bargylevych has been replaced by Andriy Gnatov, who "has been tasked with increasing the efficiency of the management."

"He is a combat guy," Zelensky said of Gnatov.

"His task is to bring more combat experience, the experience of our brigades in planning operations, defensive and offensive, as well as more active development of the corps system," he added.

"Everything that our brigades have learned from the war should be implemented one hundred percent at the planning level."

The Ukrainian military, which has grown since mobilising to repel Russia's February 2022 invasion, is in the process of reorganising its army corps to improve coordination.

Defence Minister Rustem Umerov said on his Facebook page: "We are systematically transforming the Armed Forces of Ukraine to enhance their combat effectiveness.

"This involves restructuring the command system and implementing clear standards."

Gnatov, he said, had "more than 27 years of military experience".

Bargylevych has been appointed as the chief inspector of the defence ministry, he added.

In the eastern region of Donetsk, the epicentre of the fighting, the larger and better equipped Russian army has been advancing slowly for more than a year, despite heavy losses.