Yevgeny Prigozhin, leader of the Wagner Group, said on Saturday that the headquarters of the Southern Military District and all military facilities in Rostov-on-Don were under his control.

Prigozhin in a video demanded that Kremlin bring him Chief of the General Staff Valery Gerasimov and Sergei Shoigu.

He also threatened in the video that he would go to Moscow.

"We will destroy anyone who stands in our way," he said in one of a series of video and audio recordings posted on social media.

He added, "We are moving forward and will go until the end."

In a joint declaration released Wednesday, the leaders of the Group of Seven reaffirmed their "unwavering commitment to the strategic objective of a free, independent, democratic and sovereign Ukraine."

"We will stand with Ukraine as it defends itself against Russian aggression, for as long as it takes," the joint declaration states.

G-7 leaders wrote in the joint declaration that they are working to "formalize" their "enduring support to Ukraine as it defends its sovereignty and territorial integrity, rebuilds its economy, protects its citizens, and pursues integration into the Euro-Atlantic community."

They also said they will "work with Ukraine" on an "enhanced package of security commitments and arrangements in case of future aggression to enable Ukraine to defend its territory and sovereignty."

The G-7 is an intergovernmental political forum consisting of Canada, France, Germany, Italy, Japan, the United Kingdom and the United States.

-ABC News' Ellie Kaufman