An Israeli raid last week has reduced one of Gaza’s biggest hospitals to little more than a shelter for a small, terrified crew of patients and medical staff, while health officials warned on Monday that food and fuel supplies were almost gone at another hospital that has endured a nearly monthlong siege in the same city, Khan Younis.

Israel says it is rooting out Hamas activity at the medical centers, which it says Hamas has used to hide military operations — accusations it has made about multiple hospitals in Gaza, backing up some claims with evidence of Hamas tunnels. Hamas and health officials deny those charges, and aid groups have called on Israel to respect international laws protecting hospitals from attack.

It was not possible to verify statements made by either the Israeli military or the health ministry.

At Nasser Medical Complex, Gaza’s second-largest hospital, 14 patients were evacuated in a United Nations mission on Sunday, the World Health Organization said. The Palestine Red Crescent Society said 18 more were evacuated on Monday. The United Nations said negotiations were continuing for the Israeli military to allow the remaining patients — numbering more than 150, according to the World Health Organization — to be evacuated.

The exodus was prompted by a raid on Thursday by Israeli troops who entered the hospital and detained what Israel said was hundreds of people, including some it said had taken part in the Hamas-led Oct. 7 attack on Israel. Thousands of displaced Palestinians sheltering there evacuated before and during the raid.

Caring for the remaining patients are 15 health care workers, with no tap water, little food and oxygen, few medical supplies and no electricity except a backup generator that maintains some lifesaving equipment, the W.H.O. said. The W.H.O.’s director general, Tedros Adhanom Ghebreyesus, said on Sunday that Nasser was no longer functional.