The head of Russian mercenary group Wagner, Yevgeny Prigozhin, warned Sunday that a Ukrainian counteroffensive could turn into a "tragedy" for Russia and complained that his fighters lacked ammunition.
For months Wagner has spearheaded the Russian attack on Bakhmut, the east Ukrainian town at the epicentre of fighting.
Prigozhin is an ally of President Vladimir Putin but as head of the private military group has been involved in a power struggle with Russia's defence ministry.
"We (Wagner) have only 10-15 percent of the shells that we need," he said, blaming the leadership of the Russian army.
He spoke in an interview to Russian pro-Kremlin war correspondent Semyon Pegov.
Prigozhin said he expected a Ukrainian counterattack in mid-May.
"This counteroffensive could become a tragedy for our country," he said.
Ukraine said recently that it was finalising preparations for a long-expected counteroffensive.
On Sunday, the governor of Russia's western Bryansk region said Ukraine had shelled a border village, killing four people and wounding two others.
A day earlier, a suspected drone hit a fuel depot in Moscow-annexed Crimea.