At least 274 people were killed in central Gaza on Saturday as the Israeli military moved into the Nuseirat camp to rescue four hostages, the Hamas-run Gaza Health Ministry said Sunday.

Another 698 people were injured as Israeli forces entered the refugee camp, the ministry said.

Some of the injured were in critical condition, the ministry said.

The death toll in Gaza climbed on Saturday to 37,084 people, the ministry said. More than 84,000 others have been injured, the ministry said.

-ABC News’ Victoria Beaule and Kevin Shalvey

U.S. Central Command (USCENTCOM) announced Saturday that it began delivery of humanitarian assistance ashore in Gaza.

"Today, a total of approximately 492 metric tons (~1.1 million pounds) of much needed humanitarian assistance was delivered to the people of Gaza," CENTCOM said in a statement.

No U.S. personnel went ashore to Gaza, according to CENTCOM.

The agency said it has so far assisted in the delivery of more than 1,573 metric tons of humanitarian aid to organizations operating on the ground in Gaza.

-ABC News' Nathan Luna

Secretary of State Antony Blinken released a statement Saturday following the rescue of four Israeli hostages, welcoming their safe return.

"The United States will not rest until every hostage is returned home," he said.

Blinken also pushed for the cease-fire announced last week by President Joe Biden.

He contended would "bring relief to both the people of Gaza and the remaining hostages and their families through an immediate ceasefire that could lead to the release of all hostages, a surge of humanitarian assistance, Gaza’s reconstruction, and an enduring end to the war."

"The only thing standing in the way of achieving this ceasefire is Hamas. It is time for them to accept the deal," he said.

A U.S. defense official provided ABC News with some more details about the operation.

The official said the recently constructed JLOTS pier, which is used for transporting humanitarian supplies, was not used in the operation.

"An area south of the facility was used to safely return the hostages to Israel. Any such claim to the contrary is false," the official said.

-ABC News' Nathan Luna

After meeting with rescued hostages and their families, Israeli Prime Minister Benjamin Netanyahu called the rescue operation "remarkable" and told reporters they will do "whatever it takes" to get the hostages back.

"We're committed to getting the release of all the hostages, and we expect Hamas to release them all — but if they don't, we'll do whatever it takes to get them all back home. Hamas is committing war crimes every day, including the holding of these hostage.s. Our soldiers are performing in the most valiant and moral way to end this war with a victory against these killers and against these kidnappers, and we shall prevail," Netanyahu said.

Earlier, the Israel Defense Forces said the hostages were being held in civilian populated areas, without any way to reach them but go through Gaza civilians, IDF spokesman Daniel Hagari told reporters. Three male hostages were held together in an apartment and a fourth female hostage was held in another apartment just over 650 feet away, Hagari said.

At least 150 Palestinians were killed in Israeli raids on Saturday, the Hamas-run Gaza Health Ministry said.

A United States official provided ABC News with more details about the rescue efforts, noting that the U.S. has been providing regular intelligence sharing and expertise on hostage recovery efforts since Oct. 7.

The official stressed there were no American boots on the ground as part of this effort.

-ABC News' Dana Savir, Bruno Nota and Molly Nagle

A weapon used in a strike on a UNRWA school sheltering displaced people on June 6 appears to be U.S.-made, three munitions experts told ABC News.

Journalist Emad Abu Shawiesh captured video of weapons fragments at the UNRWA al Sardi school building in Nuseirat in Gaza on June 6.

The weapon fragments seen in the video are consistent with the nose section of a U.S.-made GBU-39 "Small Diameter Bomb," Trevor Ball, a former U.S. Army explosive ordinance disposal specialist, told ABC News.

The GBU-39 also appeared to have been employed in a deadly strike on May 26 in Rafah, Gaza, according to Ball and another munitions expert, who asked not to be named due to the sensitivity of the issue.

Mark Hiznay, an associate director with the Crisis, Conflict and Arms Division of Human Rights Watch, told ABC News the image shows the remnants of a GBU-39.

N.R. Jenzen-Jones, a director at the consultancy Armament Research Services, said the image was consistent with the Small Diameter Bomb series.

“Given what we know about the IDF arsenal and munitions used in previous strikes, the remnants are most likely from a GBU-39 SDB and include a portion of the nose (forward section) of the bomb,” Jenzen-Jones said, adding that other munitions could have been used in the strike, which he had not yet assessed in detail.

-ABC News Chris Looft