Exhausted Russian fighters complain of conditions in eastern Ukraine

But those gains have come at a high price for the Russian invasion force, with evidence that high-level casualties are growing and that some units may be approaching exhaustion as the war moves past its 100-day mark.

As the conflict drags on, some fighters have gone public with appeals to Vladimir Putin for an investigation into battlefield conditions and whether their deployments to the front are even legal.

And in an interview, a Russian soldier who had fought near Kyiv, Kharkiv, and was now in eastern Ukraine, complained of exhaustion, saying he had even contacted a lawyer and complained that he had not seen his wife for months.

For the men on the ground, that has meant an exhausting tour of duty marked by bitter fighting against a battle-hardened enemy that is motivated to defend its homeland.

Russian state television has claimed that those soldiers should be ready to fight for their homeland, but locals have described empty streets and men in hiding to avoid a zealous recruiting campaign in Russian-controlled areas in eastern Ukraine.

Meanwhile, casualties among Russian officers are mounting. A reporter for state-run Rossiya-1 said that Maj Gen Roman Kutuzov was killed while leading forces from the Russian-controlled east into battle. If confirmed, he would be at least the fourth Russian general to have been killed in combat since February, and Ukraine claims the number is higher.

Russia has also used paid fighters to bolster its forces since the start of the war. It was estimated to have deployed between 10,000 and 20,000 mercenaries, including Wagner Group fighters, in its offensive in Donbas, a European official said in April.

Those units have also reported high-profile casualties.

Vladimir Andanov, a veteran Wagner soldier from Buryatia, was reported to have been killed in fighting in east Ukraine late last week. His death was confirmed by regional media and Russian military organisations.

He had previously fought in Syria and Donbas, where he had been accused of participation in extrajudicial killings.

Last month, two alleged Wagner Group fighters from Belarus were accused of murdering civilians near Kyiv, making them the first international mercenaries to face war crimes charges in Ukraine.