KHAN YOUNIS, Gaza Strip — The Israeli army ordered a mass evacuation of Palestinians from much of Khan Younis on Monday, a sign that troops are likely to launch a new ground assault in the Gaza Strip’s second largest city.

The order suggested that Khan Younis will be the latest target of Israel’s raids into parts of Gaza it previously invaded in the war, as it pursues regrouping Hamas militants. Much of Khan Younis was destroyed in a long assault this year, but large numbers of Palestinians have moved back in to escape another Israeli offensive in Gaza’s southernmost city, Rafah.

The order came as Israel released the director of Gaza’s main hospital after holding him for seven months without charge or trial over allegations that the facility had been used as a Hamas command center, which he and other Palestinian health officials have denied. He said he and other detainees were held under harsh conditions and tortured.

The decision to release Mohammed Abu Selmia raised questions over Israel’s claims surrounding Shifa Hospital, which Israeli forces have raided twice since the start of the war with Hamas.

His release triggered an uproar across Israel’s political spectrum. Prime Minister Benjamin Netanyhu’s office called it “a grave mistake.”

Government ministers and opposition leaders expressed outrage and insisted Abu Selmia played a role in Hamas’ alleged use of the hospital — although Israeli security services rarely unilaterally free prisoners if they have a suspicion of militant links.

The evacuation order covered the eastern half of Khan Younis and a large swath of the Gaza Strip’s southeast corner. Earlier in the day, the army said a barrage of rockets out of Gaza was fired from Khan Younis.

Israeli forces fought for weeks in Khan Younis this year and withdrew, claiming to have destroyed Hamas battalions. But in other places where the military has made similar claims, renewed raids have underscored Hamas’ capabilities.

Last week, the military ordered an evacuation from the north Gaza district of Shijaiyah and intensive fighting has followed.

Netanyahu said Monday that the military was “making progress toward ending the phase of the destruction of Hamas’ terror army.” But he said forces will continue to “target their remains going forward.”

More fighting in the Khan Younis area could further hamper Palestinians’ access to much-needed potable water. Included in the evacuation zone is a water line that Israel installed after criticism over its cutoff of water to the strip early in the war.

Also in the zone is the area surrounding the Kerem Shalom crossing, the major aid crossing to southern Gaza, and an aid route inside the territory that Israel has said it would safeguard.

Most of Gaza’s population of 2.3 million have fled their homes, with many displaced multiple times. Israeli restrictions, fighting and the breakdown of public order have hindered the delivery of humanitarian aid, fueling widespread hunger and sparking fears of famine.

In a statement calling for a cease-fire, U.N. Secretary-General Antonio Guterres said the new evacuation order “just shows yet again that no place is safe in Gaza” for Palestinian civilians.

The decision to release Abu Selmia and 54 other Palestinian detainees back into Gaza appeared to be meant to free up space in crowded detention centers. Since the start of the war, Israeli forces have detained thousands of Palestinians from Gaza and the occupied West Bank. Many are being held without charge or trial in what is known as administrative detention.

Abu Selmia said guards used batons to beat detainees and terrorized them with dogs, and some detainees had limbs amputated because of poor medical care. The allegations could not be independently confirmed.