Thirteen people were killed and 26 were injured from a blast that struck ambulances at the gate of Gaza's Al-Shifa hospital complex, according to the Hamas-run Gaza Health Ministry.

The Palestinian Red Crescent Society said the group of ambulances were returning to the hospital from a mission to transport injured people to the Gaza-Egypt Rafah border crossing.

The Israel Defense Forces said its aircraft hit an ambulance that it believes was being used by Hamas.

"We have information which demonstrates that Hamas' method of operation is to transfer terror operatives and weapons in ambulances," the IDF said.

"A number" of Hamas terrorists were killed in the blast, the IDF said.

The IDF said, "We emphasize that this area is a battle zone. Civilians in the area are repeatedly called upon to evacuate southwards for their own safety."

The U.S. Embassy in Cairo helped more than 100 U.S. citizens and family members who left Gaza for Egypt on Thursday, according to the White House. "Another large group of Americans" is expected to leave Gaza on Friday, the White House said.

The U.S. is aware of more Americans and family members who left Gaza on Thursday and didn't seek out help from the embassy in Cairo, White House press secretary Karine Jean-Pierre said.

-ABC News' Justin Ryan Gomez

Ramy ElNazer, CEO of the Egyptian Red Crescent, warned Friday that the organization is about to run out of its stock of humanitarian aid to send to Gaza.

A large explosion has been reported at Al-Shifa hospital, Gaza City's biggest hospital. An ambulance was apparently on fire following the blast.

A spokesman for the Hamas-run Gaza Health Ministry said, "We informed the Red Cross in accordance with international law that the convoy of wounded was moving via ambulances from Al-Shifa Hospital, but the occupation targeted the convoy in more than one location: in front of the hospital door, at the Ansar roundabout, and on Al-Rashid (Al-Bahr) Street leading to the south of the Gaza Strip."

Secretary of State Antony Blinken defended Israel's military actions against Hamas at a Friday news conference in Israel after meeting with Israeli leaders, saying, "This right to self-defense, indeed, this obligation to self-defense, belongs to every nation. No country could, or should, tolerate the slaughter of innocents."

Blinken said during his Friday meetings with Israeli leaders he viewed more footage from Hamas' Oct. 7 attack, describing the videos as "almost beyond the human capacity to process."

In one video, he said, a father at a kibbutz grabbed his two sons, who appeared about 10 or 11 years old, and pulled them from the house into a shelter.

The family was "followed seconds later by a terrorist who throws a grenade into that small shelter," Blinken said.

When the dad came stumbling out of the shelter, he was shot, Blinken said.

The sons then ran from the shelter into the house, crying, "Where's daddy?" he said.

The terrorist then "casually opens the refrigerator and starts to eat from it," Blinken said.

"It is striking, and in some ways, shocking, that the brutality of the slaughter has receded so quickly in the memories of so many. But not in Israel and not in America," he said.

After sharing details of the terror inflicted on Israeli children during the conflict, Blinken touched on the images of young Palestinian boys and girls pulled from the rubble of buildings.

"When I see that, when I look into their eyes through the TV screen, I see my own children," he said.