Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

More than 900 bodies of civilians were discovered in the Kyiv region following the withdrawal of Russian forces, Kyiv region Police Chief Andriy Nebytov said in a press briefing.

"I want to say that the number of killed civilians has surpassed 900 - and I emphasize, these are civilians, whose bodies we have discovered and handed over for forensic examination," Nebytov said.

He later said, "Bucha has the most significant number of victims. This suggests that the occupiers, the units, that operated in Bucha, were the most brutal. The most victims were found in Bucha, where there are more than 350 corpses."

Nebytov claimed Russian forces were forcing Ukrainians to work for Russia.

"We understand that during the occupation, the Russian army established a certain modus operandi, trying to find people who have influence over the community and force them to work for Russia," Nebytov said.

Nebytov said the bodies had been abandoned in the streets or were buried in temporary graves.

"There were two mass graves, if we can say so. There was a person, a communal worker, who worked before the war in Bucha. He stayed in the city and actually asked the occupiers to allow him to take away the people's bodies from the streets. He buried them in two graves. The first was for 40 dead people, the second for 57 dead people," Nebytov said.

He added: "Among them was one of our policemen, a criminal investigation officer, who unfortunately was also shot with a small weapon. Most of these bodies have been examined, and I want to say that 95% of the people were killed by sniper rifles or small arms. That is, we understand that during the occupation, people were shot in the streets."

-ABC News' Alexandra Faul

Senior U.S. defense officials believe Russia's sunken Moskva cruiser was hit by two Ukrainian-launched Neptune missiles, bolstering claims from Ukrainian officials on Thursday.

The officials could not confirm how many Russian crew members were injured or killed in the attack or subsequent fire and eventual sinking.

-ABC News' Matt Seyler

The U.S. received a formal diplomatic note from Russia protesting U.S. and NATO military aid to Ukraine and accused them of violating principles and potentially risking weapons falling into bad actors' hands, a U.S. official briefed on the note confirmed to ABC News.

The Russian government previously warned the U.S. and NATO against providing weapons and other military equipment. Both Russian Foreign Minister Sergei Lavrov and one of his deputies, Sergei Ryabkov, also warned that Western convoys providing military aid were "legitimate targets" for Russian attack.

The White House referred questions to the State Department, but a State Department spokesperson declined to comment on "any private diplomatic correspondence."

State Department spokesperson Ned Price also declined to confirm the report, but during an interview with CNN, said, "The Russians have said some things privately. They have said some things publicly. Nothing will dissuade us from the strategy that we've embarked on."

Another source said it shows the effectiveness of U.S. weapon deliveries and security assistance, that Russia is upset is happening.

Price also told CNN that the war in Ukraine could drag on through the end of this year into next year, something other U.S. officials, including Chairman of the Joint Chiefs of Staff Mark Milley, have warned about as well.

"It is possible ... but what we're trying to do is to shorten this conflict," Price told CNN, by providing Ukraine with "unprecedented amount of security assistance" and applying pressure on Russia.

The Washington Post first reported on the diplomatic note.

-ABC News' Conor Finnegan, Matt Seyler, Justin Gomez and Shannon Crawford

Serhiy Volyna, commander of Ukraine's 36th Marine Brigade, which is engaged in a brutal fight to defend Mariupol against invading Russian forces, has issued an urgent plea for military reinforcements or a political solution -- anything to break Russia's siege of the Ukrainian port city.

In an interview Friday with Ukrainian online newspaper Ukrayinska Pravda, the commander said the situation is critical and the fighting is fierce.

"It can be done and it must be done as soon as possible," Volyna added.

Despite Russia's relentless bombardment for more than a month, the 36th Marine Brigade along with units of the Azov Regiment, a far-right group now part of the Ukrainian military, have held down Mariupol. They have refused to surrender, vowing to fight until the end.

-ABC News' Yulia Drozd