A Russian lawmaker has said that Yevgeny Prigozhin, the leader of the private military firm Wagner Group, attempted a rebellion after he was told that his forces would not receive any support from the government.

The chairman of the defense committee of the lower house of Russian parliament, Andrey Kartapolov, made the comment on Thursday.

He said that several days before the mutiny, Prigozhin refused a demand from the Russian defense ministry to sign contracts with it.

Kartapolov said Prigozhin was then notified that the government would not provide Wagner with any funding or supplies. The lawmaker said this is an "important thing" for Prigozhin.

Kartapolov said Prigozhin eventually committed treason because of money, exorbitant ambitions and an agitated state of mind.

Kartapolov's remarks came amid a growing focus on the whereabouts of a senior Russian military figure.

Western media report that Sergei Surovikin, the deputy commander of Russia's military operations in Ukraine, had advance knowledge of Prigozhin's rebellion plans. He reportedly had close links to the Wagner leader.

Some outlets reported that Surovikin had been detained.

Meanwhile, Ukraine's military touted progress in its counteroffensive in the eastern region of Donetsk.

The General Staff of the Armed Forces of Ukraine said on Thursday that its troops had seized the strategic initiative in the Bakhmut sector and are carrying out offensive operations on a broad front.

It also said Ukrainian troops continue to put pressure on Russian forces on the flanks near Bakhmut, driving them out of occupied territories and consolidating Ukrainian positions. The Russian side said in May that its forces had taken full control of Bakhmut.

Ukraine's military intelligence head, Kyrylo Budanov, told a local media outlet on Thursday that Wagner forces were Russia's most effective combat unit, and will no longer take part in fighting on Ukrainian territory.