(NEW YORK) — As Russia continues its nearly 16-month-long invasion of neighboring Ukraine, political turmoil has erupted in Moscow while Kyiv tries to take back territory.

A feud between Yevgeny Prigozhin, head of the Russian paramilitary organization Wagner Group, and Russia’s top military brass escalated as Prigozhin’s forces left the front line in Ukraine and marched across the border to seize a key Russian city. They then marched north toward Russia’s capital, seemingly unopposed, before turning around just hours later. The short-lived rebellion was described by international observers as the most significant challenge to Russian President Vladimir Putin’s authority in his more than 20 years of rule.

Meanwhile, Ukrainian troops are in the early stages of a counteroffensive to reclaim the almost one-fifth of Ukraine’s territory that is under Russian control.

Here’s how the news is developing. All times Eastern:

Aug 25, 8:17 AM EDT
Kremlin denies role in plane crash believed to have killed Prigozhin

Russia on Friday vehemently denied having any involvement in the mysterious plane crash that is believed to have killed Wagner Group leader Yevgeny Prigozhin.

“There has been a lot of speculation around this crash [and] the tragic deaths of the plane’s passengers, among them Yevgeny Prigozhin. Of course, the West presents all this speculation from a particular angle. All of that is sheer lies,” Kremlin spokesperson Dmitry Peskov told reporters while answering questions during a press briefing. “One should rely on facts. For now, there are not many facts, they have yet to be established in the ongoing investigative procedures.”

Prigozhin, 62, was a former close ally of Russian President Vladimir Putin. His private paramilitary organization played a key role in Putin’s invasion of neighboring Ukraine before briefly launching an insurrection against the Russian military in June. Forces loyal to Prigozhin marched toward Moscow before turning back after several days.

A private jet was en route from Moscow to St. Petersburg on Wednesday when it went down near the village of Kuzhenkino in Russia’s Tver region, north of Moscow. All 10 people on board were killed. Prigozhin and Wagner Group co-founder Dmitry Utkin were among the passengers identified on a flight list, according to Russian officials.

The U.S. Department of Defense said Thursday that Prigozhin was “likely” killed in the plane crash.

Aug 24, 6:41 PM EDT
Biden calls Zelenskyy to wish Independence Day greetings

Ukrainian President Volodymyr Zelenskyy said in a Telegram post that he spoke with President Joe Biden who offered greetings on the Independence Day of Ukraine.

Zelenskyy in return thanked Biden for America’s support during the war.

“The U.S. took the lead in rallying global support for Ukraine. This crucial leadership enabled our struggle and bent the arc of history toward good,” he said.

-ABC News’ Ellie Kaufman

Aug 24, 5:11 PM EDT
Ukraine appeals to Wagner troops

In light of the presumed death of Wagner Group leader Yevgeny Prigozhin, the Ukrainian Defense Ministry put out a statement appealing to the PMC’s members.

The statement offered them “a difficult but rather logical choice: either become a stall of the [Russian] Ministry of Defense in the service of your killers commanders, or save their honor and take revenge on their executioners, going over to the side of Ukraine.”

“If you have not committed war crimes on the territory of Ukraine, then we invite you to join our ranks,” the statement said.

The defense ministry said it would guarantee any defectors “security and decent conditions.”

-ABC News’ Will Gretsky

Aug 24, 4:21 PM EDT
Several Ukrainian pilots to receive F-16 training in US

Beginning in October, the U.S. will provide F-16 training to a small number of Ukrainian pilots and maintenance teams, Pentagon press secretary Brig. Gen. Pat Ryder said Thursday.

Ryder said “several” pilots and “dozens” of aircraft maintenance personnel will begin training at Morris Air National Guard Base in Tucson, Arizona, after they receive English training in September at Lackland AFB in San Antonio, Texas. The number of pilots and personnel will be determined by Ukraine.

“Although some Ukrainian pilots have English language skills we are anticipating that all the pilots coming to the United States will require some level of additional English language instruction, given the complexities and the specialized English that’s required to fly these aircraft,” said Ryder.

Sabrina Singh, the Pentagon’s deputy press secretary, told reporters earlier this week that the U.S. was open to the idea of training on F-16’s if European countries reached capacity though she couldn’t define what numbers would constitute capacity. Ryder on Thursday also wouldn’t provide a number and said the U.S. wasn’t going to wait for the Netherlands and Denmark to reach capacity.

“We know that as the Danes and the Dutch prepare to train those pilots that at a certain point in time in the future, capacity will be reached. So preemptively acknowledging that and leaning forward in order to to assist with this effort is the impetus for why we’re doing this now,” said Ryder.

Ryder wouldn’t get into when F-16 deliveries to Ukraine might begin. Denmark’s Prime Minister said over the weekend that the first Danish F-16’s could arrive by New Year’s.

-ABC News’ Luis Martinez

Aug 24, 4:52 PM EDT
Prigozhin ‘likely’ killed in Russian plane crash, US says

Wagner Group leader Yevgency Prigozhin was “likely” killed in a plane crash near Kuzhenkino, Russia, on Wednesday, the Pentagon said.

Pentagon press secretary Brig. Gen. Pat Ryder said there is no information to suggest a surface-to-air missile brought down the plane. Nine others, including Wagner’s co-founder, Dmitry Utkin, are also presumed dead.

“We don’t have any information to indicate right now … there was some type of surface to air missile that took down the plane … we assessed that information to be inaccurate,” Ryder said.

He added, “But beyond that, I’m really just not going to have any further information. What was it, something that came … from inside the plane? Again, I don’t have any additional insight to provide on that.”

-ABC News’ Luis Martinez

Aug 24, 2:27 PM EDT
Putin addresses Yevgeny Prigozhin’s presumed death in plane crash

Russian President Vladimir Putin offered his first comments Thursday on the plane crash that presumably killed Wagner Group head Yevgeny Prigozhin and the private military company’s co-founder Dmitry Utkin along with eight others near Kuzhenkino, Russia, on Wednesday.

“As for the aviation tragedy, first of all, I want to express my sincerest condolences to the families of all the victims,” Putin said in an on-camera address, adding that Wagner Group made a “significant contribution to our common cause of fighting the neo-Nazi regime in Ukraine.”

“I knew (Yevgeny) Prigozhin for a very long time, since the early 1990s. He was a man with a complex destiny, and he made serious mistakes in life,” Putin said. “He achieved the results he needed both for himself and, when I asked him, for the common cause, as in these last months.”

Putin said of the investigation, “But what is absolutely clear — the head of the Investigative Committee reported to me this morning, they have already launched a preliminary investigation into this incident. And it will be carried out in full and to the end. There is no doubt about that here. Let’s see what the investigators say in the near future. Tests — technical and genetic tests — are being carried out now. This takes some time.”

-ABC News’ Will Gretsky

Aug 24, 1:10 PM EDT
Putin addresses Yevgeny Prigozhin’s presumed death in plane crash

Russian President Vladimir Putin offered his first comments Thursday on the plane crash that presumably killed Wagner Group head Yevgeny Prigozhin and the private military company’s co-founder Dmitry Utkin along with eight others near Kuzhenkino, Russia, on Wednesday.

“As for the aviation tragedy, first of all, I want to express my sincerest condolences to the families of all the victims,” Putin said in an on-camera address, adding that Wagner Group made a “significant contribution to our common cause of fighting the neo-Nazi regime in Ukraine.”

“I knew (Yevgeny) Prigozhin for a very long time, since the early 1990s. He was a man with a complex destiny, and he made serious mistakes in life,” Putin said. “He achieved the results he needed both for himself and, when I asked him, for the common cause, as in these last months.”

Putin said of the investigation, “But what is absolutely clear — the head of the Investigative Committee reported to me this morning, they have already launched a preliminary investigation into this incident. And it will be carried out in full and to the end. There is no doubt about that here. Let’s see what the investigators say in the near future. Tests — technical and genetic tests — are being carried out now. This takes some time.”

-ABC News’ Will Gretsky

Aug 24, 11:44 AM EDT
Wagner mercenaries observed exiting Belarus

Mercenaries with the Russian private military company Wagner Group were observed leaving Belarus where the group’s forces had set up camp since a failed rebellion against Russian military leaders in June, according to Andrii Demchenko, a spokesman for Ukraine’s State Border Guard Service.

The group’s movements were observed by Ukrainian border guards and intelligence officials, Demchenko said Thursday.

The reported exit comes a day after Wagner leader Yvegeny Prigozhin and the group’s co-founder and operations manager Dmitry Utkin were presumed to have died in a plane crash near Moscow.

-ABC News’ Will Gretsky

Aug 24, 11:44 AM EDT
Wagner mercenaries observed exiting Belarus

Mercenaries with the Russian private military company Wagner Group were observed leaving Belarus where the group’s forces had set up camp since a failed rebellion against Russian military leaders in June, according to Andrii Demchenko, a spokesman for Ukraine’s State Border Guard Service.

The group’s movements were observed by Ukrainian border guards and intelligence officials, Demchenko said Thursday.

The reported exit comes a day after Wagner leader Yvegeny Prigozhin and the group’s co-founder and operations manager Dmitry Utkin were presumed to have died in a plane crash near Moscow.

-ABC News’ Will Gretsky

Aug 24, 10:04 AM EDT
Ukrainian forces move into occupied Crimea, official says

Ukrainian troops have landed in occupied Crimea, a state defense official said on Thursday.

The landing in territory long held by Russian forces was accomplished without Ukrainian casualties, Andriy Yusov, spokesperson for the Defense Ministry, said on Telegram. Russian forces suffered personnel losses, he said.

Russia illegally annexed Crimea from Ukraine in 2014.

-ABC News’ Joe Simonetti

Aug 23, 1:16 PM EDT
Zelenskyy warns of ‘dangerous voices’ in Congress, impact of US election year

Ukrainian President Volodymyr Zelenskyy spoke out against American critics who are pushing for cuts to military support to his country stating there are “dangerous voices” in Congress and in the U.S.

Zelenskyy told reporters Wednesday that his team was in constant contact with National Security Advisor Jake Sullivan and other U.S. national security officials, stating he was “glad” Ukraine had the backing of the White House, enjoyed bipartisan support in Congress and received “a lot” of support from the American public.

However, Zelenskyy said the coming year will be “very difficult,” referring to the U.S. presidential election, which “will definitely have an impact on support for Ukraine.”

“I think we’re going to have a hard time,” Zelenskyy said.

He said the election results could be positive or negative for Ukraine.

“For our part, we will do everything to ensure that the support of the United States does not decrease…we will give all our time, our energy to constantly work with the USA,” Zelenskyy said. “I expect that our partners in the United States will continue to be our partners and friends.”

Zelenskyy said Ukraine was working on lobbying Biden for longer range missiles.

-ABC News’ Tom Buridge and Natalya Kushnir

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