The leader of of Russia's Wagner mercenary group appeared on Sunday to ditch plans to withdraw his forces from Bakhmut in eastern Ukraine after receiving promises overnight that they would get all the arms needed to capture the devastated city.

Yevgeny Prigozhin said in a new audio message that the Kremlin has promised to resupply his Wagner Private Military Company with as much ammunition and weapons as they need.

Prigozhin said that for the first time he received a response to the situation regarding the shortage of ammunition. He said on Saturday night that the relevant companies promised to deliver everything necessary to continue the offensive in Bakhmut.

"Overnight we received a combat order, for the first time in all this time," Prigozhin said. "We have been promised as much ammunition and weapons as we need to continue further operations. We have been promised that everything needed to prevent the enemy from cutting us off (from supplies) will be deployed on the flank," he added.

In addition, Russian Army Gen. Sergei Surovikin will personally deal with issues of interaction between the Wagner PMC and the Ministry of Defense, Prigozhin said. "This is the only man with the star of an army general who knows how to fight," Prigozhin said of the Russian Defense Ministry assigning Surovikin to work alongside Wagner.

Surovikin commanded Russia's Ukraine campaign for several months before the chief of the General Staff, Army Gen. Valery Gerasimov, was given overall operational command above him.

Russia is ready to use all means at its disposal to prevent anyone from encroaching on the security of the country in response to the recent drone attacks targeting the Kremlin, Russian Deputy Foreign Minister Sergey Ryabkov said in an interview on Russia's Channel One Thursday.

Ryabkov said Washington is using its "puppets" in Kyiv to stage more and more dangerous provocations.

"I think that any reasonable person in any country will understand that the United States continues its escalatory policies and uses its subordinates in Kyiv, their puppets, to stage and carry out more and more audacious, more and more dangerous, acts of provocation," he said.

He went on to say that U.S. officials may deny any responsibility and involvement in the attacks but nobody will believe them.

"We are working to prevent relations with the U.S. from plunging into the abyss of an open armed conflict. We are already standing on the edge, on the edge of this precipice," he said.

Russia’s Wagner mercenary group said it will retreat from Bakhmut because of severe shortages in ammunition, according to Yevgeny Prigozhin, the group's leader. He said his forces would withdraw on May 10, blaming Russia’s defense ministry for the retreat.

Wagner has played a crucial role for months in the fighting for Bakhmut, sustaining huge casualties. The announcement and the suggestion of bitter infighting within Russia’s military forces signals division and disorganization just as Russia is bracing for a major Ukrainian counteroffensive.

Prigozhin said he was taking the decision in retaliation against Russia’s military leadership, which he accused of deliberately starving his troops of ammunition because they are jealous of Wagner’s success.

Prigozhin and Russia’s defense ministry have been in a one-sided public feud for months. Prigozhin claims it's now reached a breaking point, delivering a blistering attack on Russia's senior military command in the video announcing the withdrawal. He accused them of being "cowards" and of denying Russians a victory in Bakhmut because of their "petty envy."

Ukrainian military officials said they did not believe Wagner forces would retreat from Bakhmut, suggesting they believed his announcement was an attempt to excuse his failure to seize the city by May 9 as he pledged. A spokesman for Ukraine's eastern command, Sergiy Cherevatyi, said Wagner was running out of fighters, not ammunition.

-ABC News' Patrick Reevell

Ukrainian President Volodymyr Zelenskyy called for a war crimes tribunal in a surprise visit to The Hague on Thursday.

"There must be accountability for this crime. And this can only be achieved through the tribunal. ... We must transform the experience of the Nuremberg trials into new operational rules. And that is why we advocate the creation of such a tribunal. We want to continue the tradition of mandatory punishment for such crimes as a guarantee of non-repetition of such aggression," Zelenskyy said.

-ABC News' Will Gretsky

Two Americans have died while volunteering to fight in Ukraine, the U.S. Department of State said Wednesday.

Edward Wilton and Grady Kurpasi died in combat during the conflict, bringing the total number of Americans killed to at least eight.

Wilton, 22, died on April 7 fighting in Bakhmut, his half brother Parker Cummings told ABC News. He was from Marianna, Florida.

Wilton served in the U.S. Army, Cummings said, and informed his half brother about his plans to fight in Ukraine through a message sent from a plane en route to Poland on April 10, 2022.

“My brother was very selfless. My brother was very honorable and traditional," Cummings told ABC News. "He cared more about freedom for all than for his own safety. Edward was a true hero and he will be missed until we see him again.”

Joshua Cropper, who told ABC News he fought with Wilton in Ukraine’s International Legion between April and early July 2022, said of Wilton: “He was so young, but immensely brave. Fearless. We’d need three guys to do any task, he's always going to have his hand up. He was as mature as anybody I've ever known.”

Kurpasi was reportedly last seen in April 2022 and was widely reported to be missing last June.

As recently as last fall, his family said they believed he was in critical condition in a Russian-controlled hospital in Donetsk, but it’s not clear exactly when he was confirmed dead or if he was ever hospitalized.

A GoFund Me page organized on behalf of Kurpasi's wife provides few details on his time in Ukraine, but states that he “ended up leading a squad into battle and was killed in action.”

“We can confirm the death of a U.S. citizen in Ukraine. We are in touch with the family and providing all possible consular assistance,” a State Department spokesperson said in a statement when asked about his case. “When a U.S. citizen dies overseas, including in Ukraine, the Department of State supports the legal representative and family of the deceased in numerous ways, including by providing information on the disposition of remains and estates and issuing a consular report of death.”

The spokesperson added: “The U.S. government takes its role in such a situation very seriously, providing all appropriate assistance through the legal representative, next of kin or their designee.”

Regarding Wilton, a State Department official confirmed that a U.S. citizen died near Bakhmut and said they're in touch with the family and providing all appropriate consular services.

-ABC News' Shannon Crawford and Chris Looft