President Joe Biden spoke with Israeli Prime Minister Benjamin Netanyahu on Sunday about the latest developments in Gaza, including the release of more hostages, the White House said.

"The President welcomed the release of hostages by Hamas over the past three days, including a young American girl. The two leaders also discussed the pause in the fighting and surge in much needed additional humanitarian assistance into Gaza," the White House said.

The Israeli prime minister's office also issued a statement following their conversation, saying they spoke with "great excitement" about the hostages who were released, including 4-year-old Abigail Idan.

"What a joy to see her with us. But on the other hand, what a pity that she returns to the reality of not having parents. She has no parents -- but she has a whole nation that embraces her and we will take care of all her needs," Netanyahu's office said.

-ABC News' Justin Ryan Gomez

Alma Avraham, an 84-year-old Israeli hostage released by Hamas Sunday, was taken to Soroka Medical Center in Beersheba in "serious condition," IDF spokesman Daniel Hagari said.

"Alma, who was returned to us in serious condition, was immediately evacuated by helicopter to the hospital. She was evacuated by IDF troops while still inside Gaza,” he said during a press conference.

Due to "medical reasons" and to ensure the safety of the hostages, 13 of them were escorted out of Gaza by special forces near the community of Be'eri, "in full coordination with Egyptian security authorities," Hagari added.

In a short statement, Soroka said Avraham is in "poor physical condition and severe clinical condition."

The IDF and General Security Service killed five senior Hamas officials in Gaza, IDF spokesman Daniel Hagari said Sunday, adding they were "key figures and key partners" in the Oct. 7 attack.

Hagari also said the war will not end until all the hostages are returned.

"This is the ethical and moral duty of every IDF soldier and the bodies of the defense establishment," he said.

Israeli Prime Minister Benjamin Netanyahu toured the Gaza Strip on Sunday and vowed the return of all of the hostages taken by the Hamas terror group, according to the prime minister's office.

Netanyahu spent time with Israeli commanders and fighters and visited one of the Hamas tunnels uncovered by Israeli forces, the prime minister's office said in a statement.

"We are here in Gaza with our heroic fighters," Netanyahu said in a video released by his office showing him wearing a helmet and flak jacket, and surrounded by Israeli soldiers. "We make every effort to return our abductees, and eventually we will return them all. We have three goals for this war: eliminate Hamas, return all our abductees, and ensure that Gaza does not become a threat to the State of Israel again."

Netanyahu added, "We continue until the end -- until victory. Nothing will stop us, and we are convinced that we have the power, the strength, the will and the determination to achieve all the war's goals, and we will."

-ABC News' Bruno Nota and Jordana Miller

Hamas announced that it will be delaying the release of Israeli hostages, accusing Israel of violating the cease-fire agreement regarding aid trucks and the agreed-upon terms for the release of Palestinians imprisoned in Israel.

The Al-Qassam Brigades -- the armed wing of Hamas -- said it had decided to delay Saturday's scheduled second round of hostage releases until Israel committed to allowing aid trucks to enter northern Gaza. Hamas was expected to release 13 Israeli hostages in exchange for the release of 39 Palestinians imprisoned in Israel on Saturday, sources told ABC News.

"The Al-Qassam Brigades decides to delay the release of the second batch of hostages until the occupation adheres to the terms of the agreement regarding the entry of relief trucks into the northern Gaza Strip, and due to its failure to adhere to the agreed-upon criteria for releasing prisoners," Al-Qassam Brigades said in a statement.

Hamas leader Osama Hamdan, who is based in Lebanon, said relief trucks that arrived in northern Gaza today were half of the number that was agreed upon.

"There are violations committed by the Israelis in implementing the terms of the truce, some of which occurred yesterday and were repeated today," Hamdan said Saturday, adding that another issue at stake was the reported shooting of two Palestinians on Friday as they tried to reach northern Gaza.

A senior Israeli political source told ABC News that Israel did not violate the agreement. The IDF said about 200 trucks carrying humanitarian aid are expected to enter Gaza today, after 200 trucks with aid entered Gaza yesterday via the Rafah crossing and delivered their cargo to international aid organizations.

The Palestinian Red Crescent said 61 trucks carrying food, water and medical supplies headed to northern Gaza on Saturday, the largest aid convoy to reach the area since the start of the war.

-ABC News' Ayat Al-Tawy, Nasser Atta, Jordana Miller