Secretary of State Antony Blinken on Monday called out Russian forces for their reported attacks of "agreed upon humanitarian corridors," urging Russia to "stop these attacks immediately," as the Biden administration continues its ongoing review of whether Russian aggression against civilians has reached the level of war crimes.
During a joint press conference with Latvian Foreign Minister Edgars Rinkēvičs, Blinken slammed Russia's ongoing "unprovoked and unjustified invasion of Ukraine," which began 12 days ago.
Since then, Blinken said, "more than 1.5 million people, mostly women and children, have had to flee Ukraine, flee their homes."
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"In the last several days, more strikes have killed and wounded civilians as they try to leave the cities that are being surrounded by Russian forces," Blinken said, pointing to the "women and children, the elderly, wounded civilians, people with disabilities" trying to "escape cities where there’s no heat, no electricity, relentless bombardment, and where they’re running out of food and medicine."
"And there continue to be reports of attacks by Russian forces on agreed upon humanitarian corridors," Blinken said, likening the invasion to the "horrific siege of Leningrad during World War II."
"The world is saying to Russia, stop these attacks immediately," Blinken said. "Let the food and medicine, let the people out safely and end this war of choice against Ukraine."
Blinken said that the United States, allies, and partners "will continue to stand with Ukraine."
"We’re searching our security systems to strengthen Ukraine’s capacity to defend itself," he said, adding that the Biden administration is "increasing humanitarian aid to the Ukrainian people, both those still inside Ukraine, and those who have had to flee."
Blinken said the U.S. is also "raising the costs on the Kremlin and all the aid and enablement for continuing this war."
Blinken said the U.S. is "bolstering" its "shared defense" with NATO.
"We and our NATO allies are prepared to meet any threat," Blinken said, adding that the U.S. will "defend every inch of NATO territory against aggression coming from anywhere, at any time."
"Our commitment to Article V, an attack on one is an attack on all, is ironclad," he added.
Blinken said that his "message on behalf of the United States" to the people of "all of the Baltics" is that the United States "is more committed than ever to standing with you, as our democracies rise to the challenge at this moment."
Blinken's comments about attacks on civilians, however, come as the Biden administration has sent mixed messages about whether Russia has committed war crimes during the ongoing invasion of Ukraine.
"We are collecting evidence of possible war crimes, human rights abuses, and violations of international humanitarian law. We support accountability using every tool available, including criminal prosecutions where appropriate," a spokesperson for the White House National Security Council told Fox News Monday. "We helped pass a resolution at the UN Human Rights Council to establish a commission of inquiry to investigate possible human rights violations by Russia and hold them accountable."
The spokesperson said that the U.S. and 44 other countries "have established an expert mission through the OSCE to investigate possible violations and abuses of international human rights and humanitarian law by Russia."
"We will support accountability using every tool available, including criminal prosecutions where appropriate," the NSC spokesperson told Fox News.
Officials told Fox News that the evidence the U.S. collects as part of that inquiry will be shared with allies and partners and with investigations underway, including the UN Human Rights Council and OSCE Expert Mission.
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Last week, when asked about whether Russia was committing war crimes, President Biden said he and his administration were monitoring the situation, but that it was too soon to make a determination.
On Friday, White House press secretary Jen Psaki was asked whether the strike on Europe’s largest nuclear plant, which is located about 350 miles southeast of Kyiv, would constitute a war crime to the U.S. government, but responded that there were still internal investigations underway.
"We have an internal review that's been ongoing prior to last night to collect evidence and data of the targeting of civilians, of the reported use of horrific weapons of war on the ground in Ukraine," Psaki said.
"That's an ongoing process. We have not made conclusions. It's a legal review and a process that goes through the administration."
The U.S. Embassy to Ukraine, however, said Friday morning that the Russians had committed a war crime.
"It is a war crime to attack a nuclear power plant. Putin's shelling of Europe's largest nuclear plant takes his reign of terror one step further," the embassy tweeted.
Russian forces put staff at the Zaporizhzhya nuclear power plant under their command and cut off their ability to communicate with Ukraine’s nuclear regulator, according to the United Nation’s International Atomic Energy Agency.
The Zaporizhzhya nuclear power plant was originally seized by Russian troops on Friday after an adjacent five-story training facility was set on fire by a Russian projectile.
"Ukraine reports that any action of plant management – including measures related to the technical operation of the six reactor units – requires prior approval by the Russian commander," the International Atomic Energy Agency said Sunday.
"In a second serious development, Ukraine has reported that the Russian forces at the site have switched off some mobile networks and the internet so that reliable information from the site cannot be obtained through the normal channels of communication."
Phone lines, emails, and fax were no longer functioning on Sunday, and mobile phone communications were poor, Ukraine's nuclear regulator told the UN agency.
The IAEA accused Russia of violating key safety guidelines governing nuclear plants, including that "operating staff must be able to fulfill their safety and security duties and have the capacity to make decisions free of undue pressure," and that there must be "reliable communications with the regulator and others."
Ukrainian President Volodymy Zelenskyy accused Russia of "nuclear terror" after the attack.
"Russian propaganda had warned in the past to cover the world in nuclear ash," Zelenskyy said, according to a translation of his remarks. "Now this isn’t just a warning, this is real."
The UN's nuclear watchdog also expressed concern about the Chernobyl nuclear plant in northern Ukraine, which was captured by Russian forces on the first day of their invasion. More than 200 technical personnel and guards at Chernobyl have not rotated since Feb. 23, the IAEA said.
Hundreds of civilians have been killed since Russian forces started bombing populated areas across Ukraine, according to numerous reports. At least one cluster munition strike reportedly hit a hospital, killing four and injuring 10.
The first Geneva Convention in 1864 outlawed assaults on medical personnel on the battlefield.
"We cannot confirm the existence of the use of cluster munitions inside Ukraine, nor can we confirm the use or existence of thermobaric weapons inside Ukraine. We've seen reports of them mobilizing their reserves," U.S. Ambassador to the United Nations Linda Thomas-Greenfield said last week. "We cannot confirm those reports. So rather than speculating about what that might indicate, I would just tell you that we've seen them, but we can't confirm those reports."
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Cluster munitions are explosives that contain smaller bombs. They can strike wide areas and raze entire civilian neighborhoods.
Ukraine’s foreign minister last week accused Russia of "war crimes" after he said Moscow had attacked a kindergarten and an orphanage, promising Ukraine would send evidence of the attacks to The Hague.
Fox News' Paul Best, Ronn Blitzer, Timothy H.J. Nerozzi, Adam Shaw, and The Associated Press contributed to this report.