Ukrainian President Volodymyr Zelenskyy outlined his agenda for the NATO summit in Vilnius in his evening address.

Zelenskyy said the Ukrainian government is "working to make the algorithm for gaining membership as clear and fast as possible."

The president also added, in regards to the summit, "there may be good weaponry-related news."

"The priorities are absolutely clear: air defense for our cities, for all communities throughout the country, we are working to create a full-fledged sky shield," he said.

-ABC News' Will Gretsky

Russian forces hit a residential neighborhood Sunday in the Orikhiv, Zaporizhzhia region by a guided aerial bomb during the distribution of humanitarian aid, Ukrainian officials said.

At least seven people were killed and 11 others were injured in the blast, according to the regional military administration.

-ABC News' Will Gretsky

Russian forces are suffering an average of 400 casualties daily, according to a report from the U.K.'s Ministry of Defence.

The report said that Russia is struggling with "a crisis of combat medical provision."

"It is likely that many dedicated military hospitals are being reserved for officer casualties," the report said.

The Ministry of Defence added that half of Russian fatalities in the last 17 months could have been prevented with proper first aid.

-ABC News' Will Gretsky

Ukraine Deputy Minister of Defense Hanna Malyar released a statement Monday with updates on the ongoing counteroffensive.

Malyar said that Ukrainian forces liberated more than 14 square kilometers of territory from Russian forces last week, the majority of which came from the south.

The minister added that Russian forces are "on the defensive" in the direction of Bakhmut.

"The defense forces of Ukraine were able to capture the main heights near Bakhmut and have been holding the fortress city under fire control for several days," Malyar said.

-ABC News' Will Gretsky

In the wake of Saturday's short-lived attempted rebellion against the Kremlin by the Wagner private military company, Mikhail Khodorkovsky, an exiled oligarch considered one of Putin’s best-known opponents, told ABC News he supports the mutiny and encourages Russians to back the leader of the mercenary group.

Once Russia’s richest man, Khodorkovsky, a Putin opposition activist, spent 10 years imprisoned after he challenged Putin, his case now considered a foundational moment for Putin’s regime.

When Wagner founder Yevgeny Prigozhin and his fighters marched on Moscow Saturday before making a sudden about-face, Khodorkovsky was notable among Russia’s pro-democracy opposition in calling on people to support Prigozhin, arguing that allowing him to remove Putin would create an opportunity for the democrats.

Khodorkovsky told ABC News he believed Prigozhin’s actions were a real coup attempt and that it had “seriously undermined” Putin’s power. He predicted that similar opportunities to collapse the regime will be launched soon.

"The blow to Putin’s reputation, to the authorities’ reputation, was absolutely fantastical," Khodorkovsky said. "Putin’s government today is, without a doubt, strongly undermined by what happened -- his authority, his ability to control the security services is seriously undermined."

Khodorkovsky said Prigozhin’s march on Moscow had undermined Putin’s popularity, showing neither ordinary Russians nor the security services were prepared to act to protect him.

“Along the entire route of Wagner's columns, no one in any way tried to hinder him (Prigozhin). Even the security forces did not try to stop him," Khodorkovsky said. “It showed that, in fact, inside the country, Putin has an absolute void."

Khodorkovsky said he did not support Prigozhin himself -- considering him a "war criminal" -- but that the democratic opposition should have sought to help him overthrow Putin, and then taken power from him after.

Khodorkovsky criticized other parts of the anti-Kremlin opposition who attacked him for calling on people to assist Prigozhin, saying he believed the opposition had “slept through” the opportunity and suggesting it should have sought to stage a rebellion in Moscow at the same time.

"There will definitely now be more such opportunities because of Putin’s weakening. But the next time we need to simply be more ready," said Khodorkovsky, who is living in exile in England. "If an uprising had started in Moscow to meet Prigozhin then a situation could have developed quite differently.

ABC News' Patrick Reevell