United Nations team leaders in Gaza were informed by their liaison officers in the Israeli military that "the entire population of Gaza north of Wadi Gaza should relocate to southern Gaza within the next 24 hours," a U.N. spokesperson said in a statement to ABC News.

"This amounts to approximately 1.1 million people," the spokesperson added.

"The United Nations considers it impossible for such a movement to take place without devastating humanitarian consequences," the spokesperson said.

-ABC News' Samy Zyara and Ellie Kaufman

Israelis in Tel Aviv held a candlelight vigil on Thursday for the victims of the Oct. 7 surprise terrorist attack by Hamas.

Ran Oren, who donated candles for the vigil, which was held around a fountain in central Tel Aviv, told Reuters that each candle donated represented each victim of the attack. He said the vigil was held in order to "light this dark moment."

Dozens of onlookers could be seen gathered around the makeshift vigil, some of them lighting candles along the fountain.

The vigil was first reported by Reuters.

Hospitals and the health system in the Gaza Strip are at a "breaking point," the UN World Health Organization said in a release Thursday.

"Hospitals have only a few hours of electricity each day as they are forced to ration depleting fuel reserves and rely on generators to sustain the most critical functions," the WHO said in the release. "Even these functions will have to cease in a few days, when fuel stocks are due to run out."

WHO said it documented 34 attacks on health care in Gaza since Saturday, Oct. 7. These attacks have resulted in "the death of 11 health workers on duty, 16 injuries and damages to 19 health facilities and 20 ambulances," the release said.

-ABC News’ Ellie Kaufman

Israeli authorities released images Thursday of babies they said were killed and burned by Hamas. The images were shown to Secretary of State Antony Blinken by Israeli Prime Minister Benjamin Netanyahu and the Israeli government during his visit to Israel.

The Israeli Foreign Ministry told ABC News the photos were taken by ZAKA, the organization that removed the bodies, in Kfar Aza, a kibbutz near the Gaza border where Israeli military officials said more than 100 people were killed by Hamas fighters.

Two Hamas officials, who did not provide their names, claimed in a video statement released Thursday that fighters were instructed to not target civilians and had tried to avoid harming them.

“Sadly the Hamas PR machine is now trying to claim that they did not target children and women specifically and that it was not their intention which is a blatant lie and a fake campaign to try and distance themselves from the massacre they carried out," the Israeli Foreign Ministry said. "That is why sadly we have to tweet pictures of babies they killed."

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