Middle East live updates: Israeli strikes kill 150 in Gaza as peace talks resume

World Health Organization Director-General Tedros Adhanom Ghebreyesus said early Monday that Gaza's beleaguered hospitals "have once again become battlegrounds and the health system is under severe threat."

Ghebreyesus said the Kamal Adwan Hospital in the north Gaza town of Beit Lahia "is out of service," following an Israeli raid which itself came after several weeks of encirclement and bombardment.

Israeli forces raided the compound on Friday, forcibly evacuating all remaining patients and staff. The Israel Defense Forces said it detained 240 alleged militants, among them hospital director Dr. Hossam Abu Safiya. The IDF said the hospital was a "command center" for Hamas "military operations" in the surrounding area.

Ghebreyesus said Safiya's "whereabouts are unknown. We call for his immediate release."

Kamal Adwan patients were transferred to the Al-Shifa Hospital in Gaza City and the Indonesian Hospital in Beit Lahia, both of which have also reported repeated Israeli attacks. The latter "is itself out of function," Ghebreyesus said.

"Seven patients along with 15 caregivers and health workers remain at the severely damaged Indonesian Hospital, which has no ability to provide care," he added.

Four patients were detained by the IDF during their transfer out of Kamal Adwan Hospital, the WHO chief said.

Two other facilities -- the Al-Ahli Hospital and Al-Wafa Rehabilitation Hospital in Gaza City -- were also attacked and sustained damage on Monday, Ghebreyesus said.

"We repeat: stop attacks on hospitals," he wrote. "People in Gaza need access to health care. Humanitarians need access to provide health aid. Ceasefire!"

The family of Dr. Hussam Abu Safiya, the director of Kamal Adwan Hospital in the Gaza Strip, is pleading with the international community to help learn his whereabouts, alleging he was detained by Israeli forces during a recent raid on the medical facility.

The family posted a message on Abu Safiya's official Instagram page, on which the doctor had been posting updates about the hospital's functioning, pleading, "We do not know the fate of our father."

"We appeal to every compassionate individual and all international organizations and institutions to take action," said the family, asking the international community to apply media pressure and make appeals to "help us push for his swift release from captivity."

The message said Abu Safiya is still recovering from injuries he suffered a month ago while working at the hospital.

The Israel Defense Forces said in a statement released on Saturday that Abu Safiya is suspected of being a Hamas terrorist and is being held in Gaza.

Abu Safiya had not been arrested in previous IDF raids of the hospital.

-ABC News' Camilla Alcini and Nadine Shubailat

The IDF released a statement outlining their operations in and around Kamal Adwan Hospital in the last few days.

The Israel Defense Forces said the hospital was a "command center" for Hamas "military operations in Jabaliya," although the statement and attached media do not provide corroborating evidence of this.

The statement says the IDF faced heavy fighting in areas near the hospital, and says the IDF detained 240 terrorists, including the director of the hospital, Dr. Hussam Abu Safiya, whom it says is is "suspected of being a Hamas terrorist operative.”

Abu Safiya was one of the only male staff members at the hospital not detained during the IDF's raid of the hospital in October, and he would have helped coordinate numerous resupply and patient evacuations with Israel over the last several months.

Kamal Adwan is the last functioning hospital in northern Gaza and is operating at a limited capacity due to a lack of medical supplies and the repeated attacks on the hospital.

-ABC News’ Victoria Beaule