The Israel Defense Forces said Thursday that it's responsible for Israel's security and said they failed on Saturday.

The IDF said they'll investigate how the security failure happened, but right now, they're in a time of war.

Fabrizio Carboni, regional director for Near and Middle East for the International Committee of the Red Cross, said hospitals are losing power as Gaza loses power, risking the lives of the elderly on oxygen and newborns in incubators.

"Kidney dialysis stops, and X-rays can’t be taken," Carboni said. "Without electricity, hospitals risk turning into morgues."

Defense Secretary Lloyd Austin told reporters in Brussels Thursday that the U.S. is not placing conditions on its military aid to Israel.

Austin said Israel is "a professional military led by professional leadership" and "we would hope and expect that they would do the right things in the prosecution of their campaign."

Austin said U.S. intelligence had no indication or warning that Hamas was planning such an attack.

Echoing other administration officials, Austin said, "We've not seen any indication that Iran was involved in the planning or the execution of this attack," though he added the U.S. will continue to focus on whether that is truly the case.

Austin said that the U.S. will "work urgently to get Israel what it needs to defend itself," including munitions and Iron Dome interceptors, and said helping Israel won’t affect the U.S. flow of military aid to Ukraine.

-ABC News' Luis Martinez

Israeli airline El Al said it'll fly on Shabbat -- which is from Friday night to Saturday night -- this weekend for the first time since 1982.

The flights from New York and Bangkok will bring soldiers to Israel.

Human Rights Watch has accused Israel of using white phosphorus munitions in military operations in Gaza on Wednesday, saying it violated international humanitarian law by putting civilians at unnecessary risk.

In a report released Thursday, Human Rights Watch said it based its determination on a video it said it has verified, as well as two eyewitness accounts.

The Israel Defense Forces said in a statement to ABC News that claims they used white phosphorus in Gaza are "unequivocally false."

ABC News geolocated a video showing a jellyfish-shaped plume of white smoke over the port of Gaza. The video was posted on Wednesday by the official Palestinian news agency WAFA and matches images posted on social media and by other news outlets on the day.

Two experts -- Amael Kotlarski, the weapons team manager for the defense intelligence firm Janes, and Amnesty International weapons investigator Brian Castner -- told ABC News that images suggested munitions deployed over the port of Gaza on Wednesday appeared to contain white phosphorus.

"We have verified that Israeli artillery forces striking Gaza are equipped with M825 and M825A1155mm white phosphorus projectiles," Castner told ABC News, pointing to photographs by an Anadolu Agency photographer taken on Monday and showing Israeli troops handling shells labeled "M825A1."

Kotlarski said visual evidence alone was not sufficient to confirm that these specific shells were used in the Gaza port strikes.

There are "perfectly legal" military uses for white phosphorus munitions, Kotlarski said, including to create a smoke screen to conceal movements, to mark targets for artillery or air strikes, or to illuminate a battlefield. However, its use in urban areas is "problematic due to the higher risk of collateral damage," Kotlarski said, including the munitions' potential to cause severe burns.

White House Principal Deputy Press Secretary Olivia Dalton said Friday the U.S. had not independently verified allegations Israel used white phosphorous "so that is not something I would want to speculate about or weigh in on at this time."

-ABC News' Christopher Looft, Ben Gittleson and Jordana Miller