The Kremlin on Wednesday acknowledged for the first time that a plane carrying Yevgeny Prigozhin, mercenary chief of the paramilitary Wagner Group, was possibly downed on purpose.

Kremlin spokesman Dmitry Peskov told reporters that investigators are looking into the possibility that the 62-year-old Prigozhin was assassinated.

"It is obvious that different versions are being considered, including the version -- you know what we are talking about -- let's say, a deliberate atrocity," Peskov said when asked about the investigation.

The plane carrying Prigozhin and nine others crashed in Russia's Tver region on Aug. 23, killing everyone aboard, according to the press service of Russia's Federal Air Transport Agency.

The crash came about a month after Prigozhin led a chaotic armed rebellion that threatened the longstanding leadership of Russian President Vladimir Putin.

On Friday, Peskov denied speculation that the Kremlin was involved in the plane crash, calling the allegation an "absolute lie."

The crash investigation is being conducted by the Russian Investigative Committee as a domestic incident and Peskov said that allowing in international investigators "is out of the question."

-ABC News' Will Gretsky

Ukraine conducted a massive drone attack in Crimea Thursday night into Friday morning, Ukraine Defense Intelligence spokesman Andrii Yusov told ABC News.

An attack was made on the Russian 126th Separate Guards Coastal Defense Brigade of the Black Sea Fleet in the village of Perevalne, Yusov said.

"We are still calculating enemy losses at the moment," Yusov said

-ABC News' Ellie Kaufman

The explosion that downed a plane carrying Wagner Group leader Yevgeny Prigozhin and nine others in Russia was likely caused by a bomb, two U.S. officials told ABC News on Friday.

A senior U.S. official said the preliminary belief is that the private jet was downed Wednesday by an explosion on board, potentially caused by a well-placed bomb.

Another U.S official said the United States believes that a bomb was very likely the cause of the explosion.

-ABC News' Josh Margolin and Luis Martinez

Russian President Vladimir Putin had no recent meetings with Yevgeny Prigozhin, Kremlin spokesman Dmitry Peskov said Friday.

We don't know yet how long the investigation procedures will be," Peskov said when asked if Putin will attend Prigozhin's funeral.

"The president has a busy schedule in general," he added.

Peskov would not comment on the cause of the plane crash.

-ABC News' Anastasia Bagaeva and Ellie Kaufman

Ukrainian President Volodymyr Zelenskyy and U.S. President Joe Biden are set to meet in Lithuania’s capital on Wednesday afternoon, a day after NATO leaders announced during a summit that Ukraine will be allowed to join the alliance "when allies agree and conditions are met" but didn't offer a timeline.

Earlier Wednesday, Zelenskyy held a joint press conference with NATO Secretary-General Jens Stoltenberg, fielding many questions from reporters about Ukraine's path to NATO membership. The Ukrainian president took a noticeably softer tone compared to his remarks the previous day criticizing the lack of a timeline as "unprecedented and absurd."

Zelenskyy told reporters it's difficult as NATO partners are living under different conditions, whereas in Ukraine "survival" matters. He said he understands some people are "afraid" to talk about Ukraine joining NATO because "nobody is willing to have a world war." He acknowledged that his country cannot be a member of the alliance while a war is going on within its borders, but he said "signals are important."

When asked about his upcoming meeting with Biden and how he plans to convince the U.S. president that Ukraine is ready for NATO membership, Zelenskyy responded with gratitude to the United States and confidence that Ukraine will join the alliance once Russia's war is over.

"I'm grateful to President Biden and to the Congress and to the people of United States that are truly the leaders in support and assistance to Ukraine. We highly appreciate this," the Ukrainian president told reporters. "Not planning to find any arguments for making sure that President Biden would see us in NATO. I believe that those arguments, they should be mutual because it's all about this security, the East, the European continent, the Eastern Flank of NATO. And I believe that NATO needs us just as we need NATO. And I believe that this is absolutely fair. I am confident that after the war, Ukraine will be in NATO. We will be doing everything possible to make it happen so that we with the United States would have a same understanding and same vision."

-ABC News' Molly Nagle and Joe Simonetti