U.S. envoy Linda Thomas-Greenfield addressed the Security Council Friday, warning that, "the world narrowly averted a nuclear catastrophe last night. We all waited to exhale as we watched the horrific situation unfold in real time."

She called Russia's attack on the Zaporizhzhia nuclear power plant "incredibly reckless and dangerous" and said it "threatened the safety of civilians across Russia, Ukraine and Europe."

Thomas-Greenfield urged Russia to withdraw troops from the facility, give operators full access to ensure continued safe operation and assess any damage and to halt any further use of force near Ukraine's nuclear facilities.

She said Russia has killed "thousands of Ukrainians" and "thousands" of Russian soldiers have been killed as well, adding, "President Putin must stop this humanitarian catastrophe by ending this war."

She called on Russia's envoy in the chamber to "say this won't happen again."

International Atomic Energy Agency Director General Rafael Grossi attended the meeting remotely, saying the agency was ready to deploy to Ukraine and establish "basic principles of safety and security starting with the physical integrity" of its nuclear power plants.

Ukraine has requested direct assistance, he said, calling it his agency's "duty" to assist.

The IAEA remains in contact with Ukrainian authorities, including Ukraine's nuclear regulatory agency and the company operating the facility, he said.

-ABC News' Conor Finnegan

Russia's state censor announced Friday it is blocking Facebook in the country.

The state censor, Roskomnadzor, claimed it was taking the step because of alleged freedom of speech violations by Facebook, citing the blocking of several Russian state media channels from the social media platform.

This is part of a broader push by Russian authorities to shut down independent media and social media platforms that might spread dissent against the war in Ukraine.

On Friday, the BBC announced it is temporarily pausing reporting from Russia because of a new law that imposes 15 years in jail for anyone spreading information the authorities claim is “fake” about the war in Ukraine.

-ABC News' Patrick Reevell

Approximately 100,000 children in Ukraine were raised in institutions prior to the war, according to government statistics, a United Nations Children's Fund spokesperson told ABC News.

The spokesperson said many of these institutions are located in hot spots.

These institutions are being evacuated without proper monitoring of the children's situation, according to UNICEF.

The spokesperson said many of the children in institutions like boarding schools and orphanages have disabilities.

- ABC News' Zoe Magee

A senior U.S. defense official told reporters Friday that there is still "no appreciable movement" by a convoy of Russian forces approaching Kyiv, with the closest forces still about 25 kilometers from the city.

The official said a sabotaged bridge and Ukrainian attacks have contributed to the stalling of the convoy.

As for Kharkiv and Cherniv, the official said the U.S. estimates that Russian forces are about 10 kilometers from both city centers.

The official confirmed Russia took control of the Zaparozhye nuclear power plant.

The official said the U.S. is not in a position to independently verify that Russia has taken control of Kherson, saying fighting between the Russians and Ukrainians around the city has been seen as recently as today.

Mariupol is still under Ukrainian control, but Russians are bombarding the city and approaching from the north and up from the Azov coast, the official said.

Ukraine is still assessed to have "a strong majority" of its combat air power in tact, according to the official. Both Ukraine and Russia are also both believed to be using drones.

Russia has sent in approximately 92% of the forces it had arrayed at the border, up from about 90% yesterday, the official said.

Russians have now fired more than 500 missiles against Ukraine, according to the official.

-ABC News' Matt Seyler