Yevgeny Prigozhin, leader of Russia's Wagner Group mercenary force, said on Wednesday that he believed a promised counter-offensive by Ukrainian troops had already begun and that his forces were observing heightened activity along the front.
In an audio message published by his press service on social media, Prigozhin said that the "active phase" of the counteroffensive would begin in the coming days.
The Kyiv government has long promised a counteroffensive to start taking back territory in the east that Russia annexed after invading in February 2022.
"I believe the advance of the Ukrainian army has already begun ... We are seeing the greatest possible activity both on the perimeter and within the front lines," Prigozhin said.
"I therefore believe that it has all already started. And I believe it will all enter an active phase in the very near future. It could be a matter of days."
Prigozhin later said his forces had advanced 230 metres (700 feet) in fighting that has engulfed the eastern Ukrainian town of Bakhmut. The shattered town, once home to 70,000, has been under siege for nearly 10 months.
Prigozhin said Ukrainian forces were now confined to an area in the town making up only 2.64 sq km. (about one sq. mile).
Reuters was not able to verify the battlefield reports.
Prigozhin repeated his complaint that Moscow was ignoring his pleas to increase supplies of shells.
"The ministry of defence has not provided us with artillery ammunition and we only have resources for a few days," Prigozhin said. "They ignore all requests from Wagner."
(Reporting by Reuters, editing by Ron Popeski, David Ljunggren and Grant McCool)