Israel's military reported gun battles Monday between troops and fighters on the grounds of Gaza's Al-Shifa hospital, where troops launched a raid they said targeted senior Hamas militants.
Hours into the operation, Israel urged people to evacuate from the neighbourhood around the territory's biggest medical centre, a complex crowded with patients and displaced people.
The latest military operation involving Al-Shifa triggered alarm from the World Health Organization.
"We are terribly worried about the situation at Al-Shifa Hospital in northern Gaza," WHO chief Tedros Adhanom Ghebreyesus wrote on X, formerly Twitter. "Hospitals should never be battlegrounds."
An AFP journalist witnessed air strikes on buildings in the area around the hospital and reported seeing "hundreds of people, mostly children, women, and the elderly, fleeing their homes."
Israel has repeatedly said the complex housed an underground Hamas control base -- which is denied by the militants -- and an army raid in November sparked an international outcry.
Tedros said that Al-Shifa had "only recently restored minimal health services".
Most of Gaza's hospitals are no longer functioning, according to the United Nations.
"Over the past few hours, the troops identified terrorist fire toward them from a number of hospital buildings. The forces engaged the terrorists," Israel's military said.
Israeli authorities reported the clashes on the Al-Shifa compound resulted in the "elimination" of Fayq al-Mabhouh, a man they identified as a Hamas internal security official.
"Numerous weapons were located in the room adjacent to where he was eliminated," the military said.
According to a police source in Hamas-run Gaza, who confirmed his death, al-Mabhouh was a brigadier general in the territory's police.
Fayq al-Mabhouh is the brother of Mahmoud al-Mabhouh, one of the founders of the armed wing of Hamas, according to the mens' family. Mahmoud al-Mabhouh was killed in 2010 in Dubai, in a hit which United Arab Emirates investigators suspected was the work of Mossad, the Israeli spy agency.
Israeli government spokesman Avi Hyman said the operation at Al-Shifa resulted in the detention of "tens of Hamas terrorists".
In January Israel's army said it had "completed the dismantling" of Hamas's command structure in the northern Gaza Strip, and Palestinian militants were operating in the area only sporadically.
The military has carried out operations at other hospitals in Gaza since war broke out on October 7, when Hamas militants attacked Israel from Gaza.
Hamas's unprecedented attack resulted in about 1,160 deaths in Israel, mostly civilians, according to an AFP tally based on official Israeli figures.
The militants also seized about 250 hostages, of whom Israel believes 130 remain in Gaza, including 33 who are presumed dead.
Israel has carried out a relentless bombing campaign and ground offensive that Gaza's health ministry says has killed at least 31,726 people, most of them women and children.
