More than a dozen children with cancer or other serious blood disorders have been safely evacuated from Gaza after weeks of difficult negotiations involving the U.S., Egypt, Israel and Hamas — but more than 30 remain in the war-torn territory, three doctors involved in the effort tell NBC News.

The children, accompanied by parents or companions, were evacuated from the Al-Rantisi Specialized Hospital for Children to hospitals in Egypt and Jordan, the St. Jude Children’s Research Hospital and the World Health Organization said Friday.

The development comes as hospitals across northern Gaza on Thursday and Friday came under munitions fire and as Israeli military vehicles drew near. Strikes hit the strip’s largest hospital, Al-Shifa, though it is unclear where the projectile originated.

More than 11,000 people, including 4,500 children, have died in Gaza since Israel began retaliating against Hamas, designated a terror group by the U.S. and E.U., after it launched its Oct. 7 attack that killed 1,400 people and saw more than 225 people taken hostage.

‘The heart of the war zone’

Al-Rantisi, the last pediatric hospital in north Gaza, closed late Thursday night following repeated warnings from the Israel Defense Forces to evacuate.

The day before, the IDF dropped leaflets saying: “to all those currently staying at Rantisi Hospital: The IDF is informing you that there is Hamas terror activity and infrastructure inside the premises of the hospital and its surroundings which do not enable you to remain in the premises. The hospital is in the heart of the war zone — you must move south of the Gaza river — the crossing south is open. For your safety — do not stay in the premises of the hospital in the coming hours.” The IDF has not provided evidence that Hamas operates from the hospital.

Dr. Mustafa Al-Kahlot, Al-Rantisi’s director, told NBC News at least one child was killed in strikes and more were trapped. “We were bombed twice,” he said. “The first was at the hospital gate and the second was directly on the departments.”

Tanks were seen near Al-Rantisi in videos posted on social media and geolocated by NBC News.

Officials at Al-Rantisi alerted the Palestine Children’s Relief Fund, an international nonprofit that has been providing medical assistance to the West Bank and Gaza for 30 years, said that the hospital received calls from the IDF warning there would be violence in the area and to evacuate.

Secret rescue mission

The World Health Organization and St. Jude’s had already launched a secret operation to rescue the children, and on Friday made the announcement that some of the children were safe in Egypt.

Dr. Zeena Salman, a member of the Palestine Children’s Relief Fund’s medical advisory board, told NBC news that the hospital received the warning call from the IDF at 7:45 local time Thursday evening. The hospital staff told her they felt trapped and feared getting hit by shelling if they walked out, and several of the remaining children at the hospital could not walk because they were in ICU beds on dialysis, ventilators or chemo.

“The remaining children were pushed out onto the streets Friday morning local time and we don’t know what happened to them,” Steve Sosebee, founder and president of the PCRF, said. He added that some of the children were in wheelchairs and there was no communication because of the lack of cellphone service.

Sosebee said that several other Gaza hospitals are now out of fuel, including the Indonesian Hospital that has new operating theaters his organization helped build.

The crisis for the children began almost immediately after the war broke out: Once Israel imposed an initial siege on humanitarian supplies, Al-Rantisi began to run out of fuel to generate electricity for medical equipment as well as reserves of cancer treatment drugs.

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International health care advocates appealed to the White House for help. Secretary of State Antony Blinken called on Israel to let aid in and people out, and the National Security Council and U.S. Embassies in Cairo, Jerusalem and Jordan became involved in trying to make complex arrangements for the safe passage of the young patients, according to two officials familiar with the matter.

However, there were numerous setbacks while arranging the departure of the children and their parents through the Rafah border crossing into Egypt.

Advocates including the Palestine Children’s Relief Fund had argued that the pediatric cancer patients should be included with the first group of Americans exiting Gaza though the crossing. But the crossing remained shut for more than a week after the State Department told Americans in Gaza to start moving toward the gate.

Thwarted plans

Diplomatic sources say Hamas first wanted the initial group of Americans to also include wounded Palestinians, according to two U.S. officials. But Israel and Egypt vetted the Hamas list, and the officials say it included wounded Hamas fighters.

When a group — including the children with cancer — was set to depart the hospital for the trip south to the Rafah crossing 10 days ago, there was an attack near the hospital that delayed them.

Asked about that timeline, Curtis Reid, the National Security Council’s chief of staff, told NBC News: “Indeed we saw those reports as well, and I can say that for the United States, it is very important that hospitals be protected, as they are under international humanitarian law. I don’t have any specifics to share in terms of the attack that you’re mentioning, but that concerned us as well and made us focus on trying to get as many of these children out quickly so they could receive treatment in safety.”

Reid said that “immediately upon hearing about this request, the president directed us to do whatever we could do to help these civilians who were in very acute situations get out of Gaza.”

 “Some [of the children] are still trapped in the north,” Reid said, “but we are doing all we can working with governments in the region, working with international organizations and with our partners at St. Jude’s to see if we can facilitate further departures of the children that St. Jude’s is trying to help.”

Prime Minister Benjamin Netanyahu’s senior adviser Mark Regev was asked during an interview Friday on MSNBC about the Biden administration’s concerns that Israel is violating international law by firing on or near hospitals — even if Israel believes Hamas terrorists are operating in tunnels below the medical facilities.

“If a combatant uses those sites for its military machine, then immunity is no longer there,” Regev said. “And we have the right under international law to strike at it, and if Hamas uses hospitals as it does to shield its military infrastructure, they have lost their immunity. And in doing so, Hamas has committed a war crime by putting its military infrastructure underneath the hospital.”

One nurse, who declined to give her name out of concerns for her safety, remained with the children at the cancer hospital until the last moment.

At one point during a nearby munitions barrage, she pleaded for help from her international contacts.

“I swear I want to get our message and voice out,” she wrote in a text. “Speak to the White House to anyone tell them we are a cancer hospital with sick kids they are undergoing chemo and cancer treatment and on top of us is shelling.”