The United States "would support" Finland and Sweden applying to join NATO "should they choose to apply," White House press secretary Jen Psaki said on Thursday.

"We, of course, will respect whatever decision they make. Both Finland and Sweden are close and value defensive partners of the United States and of NATO," she said.

If the countries do apply, Psaki said, it "should be reassuring to the American people about our own security interests."

"Having a strong NATO alliance, a strong Western alliance, that's a defensive alliance, by the way, it is good for our security around the world, certainly having a strong partnership with a range of countries, including Sweden and Finland," she said.

-ABC News' Justin Ryan Gomez

Russian Deputy Ambassador to the United Nations Dmitry Polyanskiy told a British news podcast that Finland and Sweden officials "know the moment they become members of the NATO, it will imply certain mirror moves on the Russian side."

"If there are NATO detachments in those territories, these territories would become a target -- or a possible target -- for a strike," Polyanskiy warned.

He continued, "NATO is a very unfriendly bloc to us. … It means that Finland and Sweden all of a sudden, instead of neutral countries, become part of the enemy and they bear all the risks."

Despite repeated claims by Russian President Vladimir Putin that NATO’s expansion is a risk to Russian security, Polyanskiy insisted the addition of Finland and Sweden to the alliance would have little impact.

"I don’t think it will really be a blow to the security of Russia because these two states become members of NATO -- hopefully they won’t, but if they do it would be the worst solution for them, but not for Russia," he said. "Russia is ready to face NATO threats. Russia has made the necessary precautions for this."

The Russian Foreign Ministry said earlier that Russia "will be forced to take retaliatory steps both of military-technical and of other nature in order to stop the threats to its national security" should Finland become a NATO member.

While Britain has pledged military support for both Sweden and Finland if they were to come under attack, regardless of whether the countries are accepted into the alliance and under the umbrella of NATO's Article 5, the U.S. has yet to make a similar bridge security guarantee.

Testifying before the Senate Foreign Relations Committee on Thursday, Assistant Secretary of State for European and Eurasian Affairs Karen Donfried said, "We will surely find ways to assure Finland and Sweden, but the nature of that is still to be worked out."

-ABC News' Shannon Crawford

About 12 Russian missiles struck in and around the Kremenchuk oil refinery in central Ukraine, according to Dmytro Lunin, head of the Poltava Regional Military Administration.

No one was injured and crews have extinguished the blaze, Lunin said.

Most missiles hit the infrastructure of the refinery, which is not operating, Lunin said.

-ABC News' Irene Hnatiuk and Yuriy Zaliznyak

The United Nations said it's verified the deaths of nearly 100 children in Ukraine in April alone -- and officials believe the actual figure to be considerably higher.

"More children have been injured and faced grave violations of their rights, millions more have been displaced," UNICEF Deputy Executive Director Omar Abdi said at Thursday's U.N. Security Council meeting. "The war in Ukraine, like all wars, is a child protection and child rights crisis."

Education also "came to a standstill" when Russia invaded, Abdi said.

One in every six UNICEF-supported schools in eastern Ukraine was damaged or destroyed as of last week, Abdi said.

"These attacks must stop. All parties must honour their legal and moral obligation to protect civilians and civilian infrastructure, to respect international humanitarian and human rights law, and to ensure the rights of children are upheld," Abdi said.

-ABC News' Christine Theodorou

At least one person -- a journalist -- was killed in a rocket attack on a residential building in Kyiv on Thursday evening, ABC News has learned.

Kyiv Mayor Vitali Kilitschko said Friday that rescuers had found the body of a victim amid the rubble.

Radio Liberty, a service of the U.S.-funded Radio Free Europe/Radio Liberty, reported that one of its employees, Vira Gyrych, was killed when a Russian missile hit her apartment in the Ukrainian capital on Thursday. Her body was found beneath the wreckage Friday morning, according to the report.

Gyrych had worked as a journalist and producer for Radio Liberty's Kyiv bureau since 2018. Prior to that, she worked for leading Ukrainian television channels, according to Radio Liberty.

"The editorial staff of Radio Liberty expresses its condolences to the family of Vira Gyrych and will remember her as a bright and kind person, a true professional," Radio Liberty said in its report.

Israeli Ambassador to Ukraine Michael Brodsky also confirmed Gyrych's death in a Twitter post, saying she was a former employee of the Israeli embassy in Kyiv.

Thursday's rocket attack came as United Nations Secretary-General Antonio Guterres visited Kyiv. Five Russian missiles flew into the city, according to Ukrainian President Volodymyr Zelenskyy. At least 10 people were injured, including four who were hospitalized, according to the Kyiv City Council.