Lynne Tracy, the U.S. ambassador to Moscow, met with detained American journalist Evan Gershkovich on Monday, the ambassador's press secretary told ABC News.

Tracy met with Wall Street Journal reporter at Moscow's Lefortovo prison where he's being held, according to the press secretary.

This is the second visit between Tracy and Gershkovich since his initial detention in March.

-ABC News' Tanya Stukalova and Ellie Kaufman

Yevgeny Prigozhin, the Wagner Group leader who led the rebellion in Russia, reportedly released a new message Monday, his first in a week, to a social media account with ties to the PMC.

In a short audio message posted by Grey Zone telegram account, which believed to be run by a Wagner member that frequently posts about events on the frontline in Ukraine, Prigozhin claimed the June 24 rebellion against Moscow was aimed at "fighting traitors and mobilizing our society."

"I think we have achieved a lot of it. In the near future, I am sure that you will see our next victories at the front. Thanks guys," he allegedly said.

The Wagner Group leader said "today, more an ever, we need your support."

-ABC News' Patrick Reevell

Amid fears Russia might blow up the Zaporizhzhia nuclear power plant, Ukraine is holding drills to prepare emergency services with how to deal with a potential radioactive disaster.

ABC News was invited to the drills in the city of Zaporizhzhia this week, about 30 miles from the plant, where firefighters in hazmat gear simulated decontaminating people from radiation during an evacuation.

Emergency workers demonstrated scanning civilians with Geiger counters as they disembarked buses, stripping some civilians and hosing them with water as they lay on stretchers. Firefighters in yellow suits sprayed down vehicles and moved them through a large washer system rigged up between fire trucks.

This week, Ukraine's chief of military intelligence, Kyrylo Budanov, claimed Russia had now completed preparation to potentially sabotage the plant if it chooses.

Read more about the drills here.

-ABC News' Patrick Reevell

CIA Director Bill Burns said Yevgeny Prigozhin's mutiny showed the "corrosive effect" of President Vladimir Putin's war in Ukraine during remarks in England on Saturday.

"It is striking that Prigozhin preceded his actions with a scathing indictment of the Kremlin’s mendacious rationale for its invasion of Ukraine, and of the Russian military leadership’s conduct of the war," Burns said during a lecture to Britain's Ditchley Foundation. "The impact of those words and those actions will play out for some time, a vivid reminder of the corrosive effect of Putin’s war on his own society and his own regime."

Burns, who served as U.S. ambassador to Russia from 2005 to 2008, also noted how Russian disaffection will gnaw away at the Kremlin and that the CIA is taking this opportunity to step up its recruitment efforts in Russia.

"Disaffection with the war will continue to gnaw away at the Russian leadership, beneath the steady diet of state propaganda and practiced repression," Burns said. "That disaffection creates a once-in-a generation opportunity for us at CIA, at our core a human intelligence service. We're not letting it go to waste."

-ABC News' Cindy Smith

Ukrainian Armed Forces have yet to reach their "full potential," but two top generals exclusively told ABC News the counteroffensive is "going to plan" despite concerns from Western analysts that Ukraine is not making enough progress.

Gen. Oleksandr Tarnavskyi, who is leading the counteroffensive in the south, told ABC News' chief global affairs correspondent Martha Raddatz that the situation is "stable."

"The main thing is that we haven’t reached our full potential," Tarnavskiy said.

Ukrainian troops launched the counteroffensive a month ago, attacking on multiple axes on the southern frontline in Zaporizhzia using Western-supplied vehicles. Ukraine succeeded in piercing Russian lines at two points, liberating a string of villages, but has since been locked in ferocious fighting

Gen. Oleksandr Syrskyi, commander of the Ukrainian ground forces, told Raddatz that last month's failed rebellion by the Putin-backed PMC, the Wagner Group, wouldn't impact the fighting on the ground.

"It would be better for us if there were some negative consequences in Russia itself, but it doesn't matter for me," he said.

Asked if he was confident of retaking the key city of Bakhmut, Syrskyi said, "Yes, of course. I’m sure."

Both sides have suffered heavy casualties, according to Western officials, particularly in the south where Russia has so far conducted "relatively effective defensive operations" in the southeastern Zaporizhzhia province, the U.K. Ministry of Defense reported.

"The enemy is suffering eight times or even 10 times higher losses, especially with the number of killed troops," Syrksyi said.

-ABC News' Guy Davies and Meghan Mistry