Israel rescued four hostages alive from two locations in the heart of Nuseirat, Gaza, Israel said Saturday.

Noa Argamani, 25; Almog Meir Jan, 21; Andrey Kozlov, 27; and Shlomi Ziv, 40, were kidnapped by Hamas from the 'Nova' music festival on Oct. 7, according to the Israel Defense Forces.

The rescues come after a morning of strikes in Central Gaza. Videos show dozens of people in the emergency department at Al Aqsa Martyrs hospital, the region's only functioning hospital.

Hamas called it an "unprecedented brutal attack" and said there are "dozens of martyrs and wounded in the streets" although they do not yet know how many people were killed and injured in the attack.

The rescued hostages have been transferred to the 'Sheba' Tel-HaShomer Medical Center and are in good condition, the IDF said.

-ABC News’ Victoria Beaule

Three Palestinians were killed and 15 others were injured when Israeli forces struck an UNRWA school and shelter in Al-Shati refugee camp in northern Gaza Friday, according to statements from Hamas and the Israel Defense Forces.

Israeli forces said Hamas "terrorists" were operating "from a container inside the grounds" of the school in Al-Shati.

"By targeting this school, which is affiliated with UNRWA, the number of UNRWA schools designated as shelter centers and targeted by the occupation by bombing exceeds more than 150 schools affiliated with UNRWA, in addition to the bombing of dozens of other facilities, installations, and service centers affiliated with UNRWA, which were designated for sheltering displaced people," Hamas said in a statement.

-ABC News' Sami Zayara, Diaa Ostaz and Jordana Miller

After being down for almost two weeks, the temporary pier system has once again been reattached to a beach in Gaza, Vice Admiral Brad Cooper, the deputy commander of U.S. Central Command, told reporters Friday.

"We expect to resume delivery of humanitarian assistance from the sea in the coming days,” Cooper said.

The reattachment to the beach was done by Israeli Defense Force engineers, just as was done the first time when the pier went into operation in mid-May.

During its one week of operations, 1,000 metric tons of aid equal to more than 2 million pounds came into Gaza via the pier, accounting for about 30% of all aid delivered to Gaza that week. With the re-establishment of JLOTS it will become the third route for aid into Gaza right now.

“Given its proven success, we expect to increase the volume of humanitarian assistance provided through the pier over the previous levels,” said Cooper. “We anticipate that our goal will be to deliver 500,000 pounds over the beach initially and then ramp that up soon thereafter. So essentially, essentially every day a million pounds over every two-day period.”

Aid will begin flowing shortly but for now weather conditions are being evaluated to make sure they are appropriate and everything is working properly before aid deliveries are resumed.

-ABC News’ Luis Martinez

At least 40 people were killed -- 14 of whom were children -- and at least 74 others were injured in the Israeli strike on an UNRWA school at the Nuseirat Refugee Camp, the Gaza Ministry of Health said Thursday.

Israeli officials have claimed that the strike was targeting Hamas and Islamic Jihad terrorists "hiding inside the school," IDF spokesman Daniel Hagari said during a press briefing Thursday.

The U.S. State Department said Israelis have claimed they were targeting "only one part of the building without hitting areas where civilians were sheltering," spokesperson Matt Miller said Thursday.

"At the same time, we've seen the reports on the ground. We’ve seen the videos on the ground. We've seen the claims that 14 children were killed in the strike and certainly if ... it is accurate that 14 children were killed, those aren’t terrorists. And so the government of Israel has said that they're going to release more information about this strike, including the names of those who died in it," Miller said. "We expect them to be fully transparent in making that information public."

U.N. Secretary-General Antonio Guterres condemned the strike on the school, which the U.N. said was sheltering some 6,000 internally displaced persons, in a statement.

A spokesperson for Guterres said, "He underscores that UN premises are inviolable, including during armed conflict and must be protected by all parties at all times. The Secretary-General calls on all parties to respect and protect civilians, and ensure their essential needs are met, in accordance with international humanitarian law."

-ABC News' Sami Zayara, Jordana Miller and Shannon Crawford

The Hamas military wing claimed in a statement Sunday that three hostages, including an American citizen, were killed in Saturday's rescue operation in central Gaza that was carried out by the Israel Defense Forces.

The IDF told ABC News on Sunday it had no knowledge of hostage deaths occurring during Saturday's raid on the Nuseirat refugee camp, in which four hostages were rescued.

In its statement, Hamas' Al-Qassam Brigades accused the Israeli government of being untruthful about the circumstances of the raid.

"In exchange for them, your own army killed three of your own captives in the same attack; one of them holds an American citizenship," the Al-Qassam Brigades statement said. "Time is running out. Your government is lying."

A White House National Security Council spokesperson said Sunday they have "seen nothing to corroborate" the claims that three other hostages, including an American, were killed during the raid.

"We have seen nothing to corroborate these claims. We are of course continuing to assess the claims," the spokesperson told ABC News.

At least 274 people were killed when the Israeli military moved into the Nuseirat camp to rescue hostages, the Hamas-run Gaza Health Ministry said Sunday. Israel's military said no more than 100 civilians were killed in the operation.

-ABC News' Victoria Beaulé, Jordana Miller and Michelle Stoddart