Israel and Egypt agreed to allow at least 19 sick children, most of them cancer patients, to leave Gaza for medical treatment on Thursday, Israeli and Palestinian officials said, in the first major evacuation of critically ill Gazans since the Rafah border crossing shut down in early May.

The Israeli military said the operation had been carried out in coordination with the United States, Egypt and the international community. In total, 68 people — sick and injured patients and their escorts — were allowed to leave, the military said.

Tania Hary, who directs Gisha, an Israeli nonprofit organization that advocates the free movement of Palestinians, said she was relieved that the children may “have a chance at life and finally receive the care they deserve.” But she emphasized that many more sick and wounded people remained trapped in Gaza, without any obvious mechanism for how they might be evacuated.

“It is a drop in an ocean of suffering, as thousands more wait to reach medical facilities outside the strip,” she said. “It serves as another reminder that the most vulnerable residents of Gaza — its children, sick and elderly — are paying the highest price.”

More than 10,000 sick and wounded people in Gaza require urgent care that is available only outside the enclave, the World Health Organization said this week. They include those wounded in airstrikes, as well as cancer patients, children with life-threatening illnesses and older people who need open-heart surgery.

Even before the war, many Gazans were forced to travel abroad for lifesaving treatments, like chemotherapy, which were almost nonexistent in the Gaza Strip. The enclave’s health sector has struggled for more than 15 years under a crippling Israeli-Egyptian blockade intended to contain Hamas.