(Reuters) -President Volodymyr Zelenskiy said on Monday he had replaced the commander of the Joint Forces of Ukraine's Armed Forces, Lieutenant-General Yuri Sodol, after reports surfaced that he had performed badly in the 28-month-old war against Russia.

Zelenskiy, speaking in his nightly video address, gave no reason for the dismissal. He said Sodol had been replaced by Brigadier-General Andriy Hnatov in the post, which involves strategic planning of operations.

Sodol's removal, one of a series of personnel changes, followed publication of a letter by the head of Ukraine's revered Azov regiment, Bohdan Krotevych, in which he alleged that Sodol's actions had led to serious military setbacks.

In a post on the Telegram messaging app, Krotevych did not identify Sodol by name, but said an unnamed general "has killed more Ukrainian soldiers than any Russian general."

"What I do care about is that combat battalion and brigade commanders are put on trial for losing an observation post, but a general is not put on trial for losing regions, dozens of cities and thousands of soldiers," Krotevych wrote.

"All the military personnel now understand who I am talking about because 99 percent of the military hate him for what he does."

The news outlet Ukrainska Pravda, citing a leaked report, said a criminal complaint had been submitted concerning Sodol, who was promoted earlier this year, although it did not identify him. It said Krotevych was willing to testify against him.

Hnatov had served as deputy commander of the southern theatre of operations since 2022 and played a leading role in recapturing much of southern Kherson region from Russian invaders.

In the spring of 2023 he commanded the defence of Bakhmut in eastern Ukraine, a town that eventually fell to Russian forces after many months of pitched battles.

Krotevych, in a social media post after the president's announcement, described Hnatov as a "very worthy officer".

With Russian forces making gains and slowly advancing through eastern Ukraine in recent months, the military has undergone considerable changes.

The military top commander, Valeriy Zaluzhnyi, was dismissed in February after public differences with Zelenskiy over the conduct of the war.

(Reporting by Ron Popeski and Oleksandr Kozhukhar; Editing by Chris Reese and Bill Berkrot)