United Nations Secretary-General Antonio Guterres said he was "shocked" by Thursday's killing of more than 100 people seeking humanitarian aid in the northern Gaza Strip and that it would require an effective independent investigation.

Guterres made the comments while speaking ahead of a regional summit in St. Vincent and the Grenadines later Thursday. When asked about the U.N. Security Council's repeated failure to adopt a resolution demanding a cease-fire between Israel and Hamas, Guterres told reporters that the worsening geopolitical divides have "transformed the veto power into an effective instrument of paralysis of the action of the Security Council."

"I am totally convinced that we need a humanitarian cease-fire and we need the unconditional and immediate release of hostages and that we should have a Security Council able to achieve these objectives," he added.

-ABC News' Morgan Winsor

U.S. Department of State spokesperson Matt Miller acknowledged that Thursday’s deadly incident in Gaza City "very well could" complicate hostage talks.

At least 112 people were killed and 760 others were injured when Israeli forces allegedly opened fire on hungry Palestinians who were waiting for food in Gaza City, according to a spokesperson for Gaza's Hamas-run Ministry of Health.

Israeli security officials told ABC News the crowd approached Israeli troops securing the passage of aid trucks in a manner that posed a threat to the troops, who responded with live fire. There was no use of artillery fire, airstrikes or drone strikes in the incident, according to Israeli security officials.

During a press briefing later Thursday, IDF spokesperson Rear Adm. Daniel Hagari claimed soldiers did not fire at people seeking aid.

"This terrible event underscores the urgency in bringing the hostage talks to a close," Miller told reporters Thursday. "We continue to believe a deal is possible and that the deal is in the interest of Israel, the Palestinian people and the broader region."

"When it comes to establishing facts on the ground, we are urgently seeking additional information on exactly what took place," Miller noted. "We have been in touch with the Israeli government since early this morning and understand that an investigation is underway. We will be monitoring that investigation closely and pressing for answers."

He later added that no United Nations agencies were believed to have been involved, and that the U.S. had seen "conflicting reports" from Israel and local Palestinians.

"We don't have ground truth on what happened," he said, later adding that "oftentimes the early accounts in these situations have turned out to be incorrect."

Miller also expressed "the United States' deepest condolences to the families for those who died."

"Far too many innocent Palestinians have been killed over the course of this conflict, not just today, but over the past nearly five months. And when you think about today's tragedy, it is especially heartbreaking to consider how many of those families affected will be burying loved ones not for the first time," he said.

-ABC News' Shannon Crawford

After suggesting a cease-fire between Hamas and Israel could happen by Monday, U.S. President Joe Biden is now indicating it may take longer to reach a deal, without offering a new timeline.

"Probably not by Monday, but I'm hopeful," Biden told reporters on Thursday. "Hope springs eternal."

The United States, along with Egypt and Qatar, has been mediating talks between the warring sides.

Biden spoke on the phone Thursday with the emir of Qatar and the president of Egypt. All leaders agreed that Hamas should release the hostages "without delay" and that it would result in "an immediate and sustained cease-fire in Gaza over a period of at least six weeks," according to a White House readout.

Biden also thanked Egyptian President Abdel Fattah El-Sisi for delivering humanitarian aid to Gaza and plans to surge more assistance to the region.

-ABC News' Justin Ryan Gomez

Israeli forces allegedly opened fire on hungry Palestinians who were waiting for food aid in the northern Gaza Strip on Thursday morning, according to a spokesperson for Gaza's Hamas-run Ministry of Health.

At least 112 people were killed and 760 others were injured in the incident at Al-Nabulsi roundabout near Al-Rashid Street in the southwest of Gaza City, the health ministry spokesperson said in a statement, adding that the death toll was expected to rise as dozens of the wounded were in critical or serious condition. Patients from the incident who were admitted to Al-Shifa Hospital in Gaza City suffered from injuries consistent with gunshot wounds, being hit by tank artillery shells and being trampled, according to the health ministry spokesperson.

When asked for comment, the Israel Defense Forces told ABC News on Thursday: "Early this morning, during the entry of humanitarian aid trucks into the northern Gaza Strip, Gazan residents surrounded the trucks, and looted the supplies being delivered. During the incident, dozens of Gazans were injured as a result of pushing and trampling. The incident is under review."

Israeli security officials told ABC News on Thursday that the crowd approached IDF troops securing the passage of aid trucks in a manner that posed a threat to the troops, who responded with live fire. There was no use of artillery fire, airstrikes or drone strikes in the incident, according to Israeli security officials.

Northern Gaza has been isolated by the Israeli military and almost completely cut off from humanitarian aid for weeks, according to the United Nations, which continues to warn about the threat of famine for people still living there.

One of the truck drivers who delivers humanitarian aid to northern Gaza, Ahmed Ayad, told ABC News on Wednesday that crowds of people waiting for food aid on Al-Rashid Street block the vehicles from reaching their final destination, prompting Israeli soldiers to open fire.

"They fire so that we can advance comfortably," Ayad said. "But people don't respond to the shooting, so they move toward us and take aid from the truck. They're waiting. Everyone is anxious and the amount [of food] arriving is not enough."

U.S.President Joe Biden said Thursday that the White House is looking into the reports of Israeli forces killing civilians.

"There are two complete versions of what happened. I don’t have an answer yet," Biden said, adding that this will complicate the cease-fire negotiations.

The Biden administration is considering airdropping aid into Gaza, a U.S. official told ABC News.

-ABC News' Nasser Atta, Morgan Winsor and Samy Zyara