Russia-Ukraine updates: US sanctions Russian military shipbuilder, diamond miner

About two-thirds of the Russian forces that were arrayed against the capital of Ukraine have withdrawn toward Belarus, according to a senior U.S. defense official.

The number of Russian forces being pulled back from Kyiv is up from an estimated 20% late last week, the official said.

Russian Deputy Defense Minister Col. Gen. Alexander Fomin told reporters last week that Russia's military activity was being dramatically curtailed near Kyiv and in Chernihiv in northern Ukraine in an attempt to increase "mutual trust and create conditions required" for further peace talks with Ukrainian negotiators.

The United States has been skeptical of Russia's promise to scale back its military activity near Kyiv.

Before repositioning its forces, Russia had close to 20 battalion tactical groups (BTGs) bearing down on Kyiv from the north and northwest, with each group comprised of 700 to 900 troops. Roughly 13 of those BTGs are now either in Belarus or on their way there.

The Pentagon believes the withdrawing forces will be resupplied and possibly reinforced in the north before heading back into Ukraine to fight elsewhere, the official said.

"Our best assessment –- and it is only an assessment -– is that they will be applied in the eastern part of the country in the Donbas region," the official said of the two separatist areas, Donetsk and Luhansk, in eastern Ukraine that Russian President Vladimir Putin recognized as independent self-proclaimed people's republics prior to the Feb. 24 invasion of Ukraine.

The United States has also seen some Russian troops leave the city of Sumy in northeast Ukraine and head north to the Russian border, according to the official.

Despite these movements, the official said the "vast majority" of the more than 125 BTGs that Russia committed to the invasion remain inside Ukraine.

-ABC News' Matt Seyler

Germany's foreign minister said Monday that her country is moving to expel a "significant" number of Russian diplomats following reports that Russian troops killed more than 400 civilians in the Ukraine city of Bucha.

"The pictures from Bucha bear witness to the unbelievable brutality of the Russian leadership and of those who follow its propaganda, to a will to annihilate that transcends all borders. We have to fear similar pictures from many other places that Russian troops have occupied in Ukraine," Germany's Foreign Minister Annalena Baerbock said in a statement.

Baerbock added that Germany is opposed to the inhumanity alleged in Bucha and must stand for freedom and be prepared to defend it. Baerbock said Germany, therefore, has decided to declare a significant number of the Russian diplomats persona non grata.

She said the Russian ambassador to Germany was informed of the decision on Monday afternoon.

Germany will also take further action against Russia together with allies, tightening existing sanctions, increasing support for Ukraine's armed forces and strengthening the NATO eastern flank.

The statement and corresponding tweet from Baerbock does not say how many diplomats will be expelled.

-ABC News' Christine Theodorou

The International Committee of the Red Cross said Monday that its staff has been blocked again from entering Mariupol after failing to reach the besieged Ukrainian port city for several days.

An ICRC team tasked with escorting evacuation buses to and from Mariupol "was stopped on Monday while carrying out humanitarian efforts to help lead a safe passage corridor for civilians" and is now "being held in the town of Manhush," about 12 miles west of Mariupol, according to an ICRC spokesperson.

"The ICRC has been in direct contact with our colleagues and is speaking with the parties on all sides to bring clarity to the situation and allow them to resume their humanitarian work," the spokesperson told ABC News in a statement.

-ABC News' Brian Hartman

U.S. President Joe Biden said Monday that he is seeking more sanctions against Russia after horrific images surfaced of dead civilians lying in the bombed-out streets of Bucha, Ukraine.

Upon his return to the White House from Fort McNair, Biden said he will call for more sanctions but stopped short of accusing Russia of committing genocide in Ukraine.

"I'm seeking more sanctions, yes," Biden said, declining to offer specifics when pressed.

Biden described the situation in Bucha as "outrageous" and called Russian President Vladimir Putin "brutal."

"You may remember I got criticized for calling Putin a war criminal. Well, the truth of the matter -- you saw what happened in Bucha," Biden said. "This warrants he is a war criminal. But we have to gather the information. We have to continue to provide Ukraine with weapons they need to continue the fight. And we have to gather all the details. So this could be an actual -- have a war-crime trial. This guy is brutal. And what's happening with Bucha is outrageous. And everyone sees it."

Ukrainian officials accused Russian troops of committing genocide in Bucha, which was retaken by Ukrainian forces in recent days. Ukrainian leaders said 410 civilians were killed in the fighting in Bucha and that many were found with their hands bound and shot at close range.

Asked if he thought Russia was committing genocide, Biden replied, "No, I think it is a war crime."

-ABC News' Molly Nagle

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Biden on Putin: ‘This guy is brutal’

President Biden spoke to reporters about the "outrageous" situation in Bucha, Ukraine, as horrific images emerge.