May 1, 2023 - Russia-Ukraine news

The Biden administration announced new estimated casualty figures Monday from Russia’s winter offensive in Ukraine, saying that the country has suffered more than 100,000 casualties since December and the "stunning" number is a key signal that Moscow's effort has “backfired.” 

White House official John Kirby told reporters Monday that Russia has "exhausted its military stockpiles and its armed forces" and since December, the US estimates Russia has suffered more than 100,000 casualties, including over 20,000 killed in action. 

The US is defining the term “casualty” as both wounded and killed. 

Here are the latest developments:

Dialogue between the United States and Russia on the status of detained Americans has been "irregular," US Secretary of State Antony Blinken said Monday.

Blinken called for the immediate release of detained Wall Street Journal reporter Evan Gershkovich. 

Pressed on repercussions for Moscow in response to the detention of American citizens, Blinken said the US has “taken a number of measures, including sanctions across the years and across cases.” 

Video footage taken at the scene of Monday's track explosion, which caused a freight train derailment in Bryansk, Russia, shows dozens of destroyed and burned out rail cars smoldering as emergency crews put out several fires.

Alexander Bogomaz, the region’s governor wrote on Telegram that an explosive detonated 136 kilometers (84.5 miles) along the Bryansk to Unecha railway, which borders Ukraine. He added that there are no casualties. 

"You must highlight the wretchedness of those who are doing the planning in the Ukrainian special forces. They came here and put down mines, blew up a commercial train. How vile!" said Sergey Karnaukhov, the Pro-Kremlin blogger and activist who posted videos from the scene of the incident.

CNN cannot independently verify the allegations made by Karnaukhov as to who was responsible for the derailment. Ukraine has not yet commented on the incident. 

Ukraine said it has “no knowledge” of a peace mission involving the Vatican to resolve the conflict with Russia.

The official dismissed any papal role after Pope Francis on Sunday told journalists that the Vatican is part of a mission to end the war in Ukraine. “The mission is in the course now, but it is not yet public,” he said after a three-day trip to Hungary.

“When it is public, I will reveal it,” the pope added.

Last week, Ukrainian Prime Minister Denys Shmyhal met Francis at the Vatican and said he had discussed a “peace formula” put forward by Zelensky and invited the pope to visit Ukraine.

The Biden administration announced new estimated casualty figures Monday from Russia’s winter offensive in Ukraine, saying that the country has suffered more than 100,000 casualties since December and the "stunning" number is a key signal that Moscow's effort has “backfired.” 

The US is defining the term “casualty” as both wounded and killed.  

Kirby, who serves as National Security Council coordinator for strategic communications, noted that “nearly half” of those casualties were fighters with the Russian private company Wagner — whom CNN has reported have experienced horrific experiences on the battlefield following minimal training and little leadership.

Kirby lambasted a recent assertion from Wagner leader Yevgeny Prigozhin, who said Sunday that his group had only suffered 94 casualties. Kirby called Prigozhin's comments “just a ludicrous claim.” 

Pressed on the source of the new 100,000 figure, Kirby said it was “based on some downgraded intelligence that we’ve been able to collect.” He declined to provide information on Ukrainian casualties, noting that the US has “never” provided such information and would defer to Ukraine on the matter.

Kirby added that the Ukrainians “are the victims here, Russia is the aggressor, and I'm simply not going to put information in the public domain that's going to, again, make it any harder for the Ukrainians."

The official noted that it's ultimately Ukraine's decision to declassify the information and make their casualty figures public. "I don't need to abide by that same sense of courtesy for the Russians — haven't done it and I ain't going to start now," he said.

With regards to fighting on the ground: Kirby said that “most” of Russia’s efforts have “stalled and failed” as the battle for the eastern city of Bakhmut continues. He added that Russia has made “incremental” gains in the town that has “very little strategic value.” 

“The bottom line is that Russia's attempted offensive has backfired. After months of fighting and extraordinary losses, Russia continues to be focused on a single Ukrainian city with limited strategic value," the official said.

Kirby said any decision about a spring counteroffensive from Ukraine would be “for President (Volodymyr) Zelensky to make,” but that the US will continue to provide military aid and support. 

The US official also told reporters a future package for Ukraine would be unveiled "very soon."

"What we want to stay focused on is making sure that we're helping them be as ready as they can be for whenever they choose to step off. And that means, obviously, in material support,” he told reporters.

The Ukrainian military says it is locked in a “positional struggle” as fierce fighting continues to rage in Bakhmut, adding it has been able to push back Russian forces after a series of counterattacks.

“I can definitely confirm the information that the enemy in Bakhmut left some positions after some of our counterattacks,” Serhii Cherevatyi, the spokesperson for the Eastern Grouping of the Ukrainian Armed Forces, told a national broadcaster. 

Cherevatyi added that for all its efforts, Russia still had not been able to “completely” capture Bakhmut. 

The spokesperson went on to say that although the Russian military’s airborne units had reinforced positions in Bakhmut, Wagner forces continued to be the ones carrying out the assaults. 

“However, due to heavy losses, they have been reinforced by airborne units. In addition, in an effort to capture Bakhmut completely, we also note that the enemy is also using snipers from special units and even special services (counterterrorism, for instance) to hit our positions as much as possible," he said.

Cherevatyi said Russian forces were having to be more mindful of their use of artillery shells and rockets, but rejected claims by Wagner founder and financier Yevgeny Prigozhin that his fighters were being starved of ammunition.

“They have been given a general norm of shells, just like other units of the aggressor,” he said. “Over the past 24 hours, the enemy has fired 304 times at the Lyman-Kupiansk direction with various artillery systems. However, of course, if we take the summer of 2022, they could use an unlimited amount of ammunition along the entire front line non-stop. Now they no longer have this luxury.” 

“What Prigozhin is talking about is that they are used to having a lot of ammunition. Now they are forced to limit themselves,” he added.

Cherevatyi concluded by defending Ukraine’s strategy for the region, stating that "the enemy has not been able to take Bakhmut for nine months."

“Thus, we are conducting a successful defense operation and are achieving our main goal: destroying the enemy's military potential, personnel, and equipment to the maximum extent possible," he said. "In particular, Wagner is close to being completely destroyed."

Russia unleashed a wave of missile strikes across parts of Ukraine on Monday, killing at least one person in Kherson and injuring dozens more.

In Bakhmut, the Ukrainian military says it is locked in a “positional struggle” as fierce fighting continues to rage, adding it has been able to push back Russian forces after a series of counterattacks.

Here are the latest developments:

A former US marine, Cooper “Harris” Andrews, 26, was killed on the outskirts of Bakhmut late last week, according to his mother and colleagues in Ukraine.

Andrews, from Cleveland, Ohio, was hit by a mortar, his mother, Willow Andrews said, likely on April 19 on the so-called “Road of Life” — a rare access road into Bakhmut used by the Ukrainian military to resupply their forces and also to evacuate civilians.

Andrews' body has yet to be recovered, she said, due to the ongoing fighting around Bakhmut. The city's outsized symbolic importance has led to intense fighting as Moscow desperately tries to seize it.

Andrews worked for an activist group known as the Resistance Committee, according to its social media statements. The group said he was killed assisting the evacuation of civilians from the city.

Andrews left Cleveland, Ohio in November and joined the Foreign Legion in Ukraine, a group of foreign fighters helping the Ukrainian military. His contract ended in March, his mother said, and he decided to stay on. 

The US Department of State said on Monday it could “confirm the death of a US citizen in Ukraine,” without naming the individual.

 CNN has reached out to the Ukrainian military for comment but has yet to hear back.

The Russian Defense Ministry said “all assigned targets were hit” in a deadly barrage of strikes launched against parts of Ukraine on Monday, injuring dozens of people including children.

“The Armed Forces of the Russian Federation launched a group missile attack with long-range precision weapons, air and sea based, on the military-industrial complex of Ukraine," the ministry said in a statement, adding that the country's assault on the embattled city of Bakhmut is ongoing.

Ukrainian officials reported that missile strikes in Pavlograd had injured at least 34 people, including five children.

Additionally, video circulating on social media and shared by a Russian-installed governor of the southeastern Zaporizhzhia region, Vladimir Rogov, appears to show that Russia hit an ammunition depot at a railway station in Pavlograd.

CNN has been unable to verify the videos.

CNN’s Josh Pennington contributed to this post.