DEIR AL-BALAH, Gaza Strip (AP) — Israel said Wednesday its troops retook part of a corridor that bisects Gaza, and its defense minister warned that attacks would intensify until Hamas frees dozens of hostages and gives up control of the territory.

The military said it had retaken part of the Netzarim Corridor that divides northern Gaza from the south, and from where it had previously withdrawn as part of a ceasefire that began in January. That truce was shattered Tuesday by Israeli airstrikes that killed more than 400 Palestinians, mostly women and children, according to the Gaza Health Ministry.

The advances on the ground by Israel on Wednesday — which included sending more troops to southern Gaza — threatened to drag the sides into all-out war again. The ceasefire had given war-weary Palestinians some respite, allowed a much-needed surge of humanitarian aid into Gaza — and led to the release of dozens of hostages who had been held for more than 15 months.

Within Israel, the resumption of airstrikes and ground maneuvers has raised concerns about the fate of roughly two dozen hostages held by Hamas who are believed to still be alive. Thousands of Israelis took part in anti-government demonstrations in Jerusalem, with many calling for a deal to bring the captives home.

A Hamas spokesman, Abdel-Latif al-Qanou, said the moves by ground forces in Gaza was a clear sign that Israel had backed out of the truce and was reimposing a “blockade.” There have been no reports of rocket attacks by Hamas since Tuesday's bombardment.

Also Wednesday, the United Nations said one of its employees was killed in Gaza and five others were wounded in an apparent strike on a guesthouse. It was not immediately clear who was behind the strike, the U.N. said.

Israel launches ‘limited’ ground operations in Gaza

The military said its “limited ground operation” in Gaza would create a “partial buffer between northern and southern Gaza.”

It wasn’t immediately clear whether the move would entirely block Palestinians from traveling north or south through the Netzarim Corridor.

Israel used the roughly 4-mile (6-kilometer) corridor as a military zone during the war. It ran from the Israeli border to the coast, just south of Gaza City, the territory’s largest metropolitan area.

Israel said airstrikes on Wednesday hit dozens of militants and militant sites, including the command center of a Hamas battalion. It denied Palestinian claims that it hit the U.N. guesthouse.

Fares Awad, an official in the Gaza Health Ministry, said an Israeli strike on a gathering of mourners in the northern town of Beit Lahiya killed 17 and wounded 30. The Israeli military had no immediate comment.

Israel says it will order new evacuations for Palestinians in Gaza soon

Until Israel withdrew from Netzarim in January, hundreds of thousands of Palestinians who had fled northern Gaza for the south were prevented from returning throughout the war. Many of them have since returned.

But Israel Katz, the Israeli defense minister, said the military would soon order Palestinians to evacuate from combat zones.

Katz said Tuesday's aerial bombardment “was just the first step” in Israel's plan to ratchet up the pressure on Hamas to release the remaining hostages and give up control of Gaza. Until it does, Israel will attack “with an intensity that you have not known.”

A UN worker is killed in a strike

Jorge Moreira da Silva, head of the U.N. Office for Project Services, declined to say who carried out the strike in the central city of Deir al-Balah. He said the blast was not accidental or related to demining activity.

He did not provide the nationalities of those killed and wounded.

Moreira da Silva said strikes had hit near the compound on Monday and struck it directly on Tuesday and again on Wednesday. He said the agency had contacted the Israeli military after the first strike. “Israel knew this was a U.N. premise, that people were living, staying and working there,” he said.

Lt. Col. Nadav Shoshani, a military spokesperson, said the explosion was not caused by Israeli fire.

After the strike Wednesday, the wounded were rushed to Al-Aqsa Martyrs’ Hospital in central city of Deir al-Balah. One man was carried inside on a blanket held up by medical workers. Another lay on a hospital bed, his knee bandaged.

In southern Lebanon, a U.N. peacekeeper was wounded after stepping on a mine. U.N. deputy spokesman Farhan Haq said the incident took place during “operational activity” by the peacekeeping mission known as UNIFIL in the village of Zibqin, adding that the injuries are not life-threatening.

Hundreds of Palestinians have been killed in Israel's new offensive

The Gaza Health Ministry said at least 436 people, including 183 children and 94 women, have been killed since Israel launched the strikes early Tuesday. It said another 678 people have been wounded.

The military says it only strikes militants and blames civilian deaths on Hamas because it operates in densely populated areas.

The war has killed nearly 49,000 Palestinians, according to local health officials, and displaced 90% of Gaza’s population. The Health Ministry doesn’t differentiate between civilians and militants but says over half of the dead have been women and children.

The war erupted when Hamas-led militants stormed into southern Israel on Oct 7, 2023, killing some 1,200 people, mostly civilians, and taking 251 hostages. Most have been released in ceasefires or other deals; 59 hostages remain, and more than half are believed to be dead.

Israelis protest against their government

Before this week's attacks, Israel and Hamas were set to negotiate an extension of the first phase of the ceasefire agreement, which lasted six weeks.

But those talk never got off the ground. Hamas has demanded that Israel stick to the terms of the initial ceasefire deal, including a full withdrawal from Gaza and an end to the war. Israel, which has vowed to defeat Hamas, has put forward a new proposal that would extend the truce and free more hostages held by Hamas, without a commitment to end the war.

The breakdown of the ceasefire was met with anger in Israel, where many support the plight of the hostage families to free their loved ones.

Israel's return to a military campaign came as Netanyahu faces mounting domestic pressure, with mass protests taking place over his handling of the hostage crisis and his plan to fire the head of Israel's internal security agency. Demonstrators massed around Israel's parliament on Wednesday and later marched near Netanyahu's residence in Jerusalem, where police sprayed water to try to clear them.

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Frankel reported from Jerusalem and Magdy from Cairo.

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Follow AP's war coverage at https://apnews.com/hub/israel-hamas-war

An Israeli tank takes position on the Gaza Strip border in southern Israel, Wednesday, March 19, 2025. (AP Photo/Ariel Schalit)

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Displaced Palestinians, carrying their belongings traveling from Beit Hanoun to Jabaliya, a day after Israel's renewed offensive in the Gaza Strip, Wednesday, March 19, 2025. (AP Photo/Jehad Alshrafi)

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Displaced Palestinians set up tents next to the Indonesian Hospital in northern Gaza, a day after Israel's renewed offensive, Wednesday, March 19, 2025. (AP Photo/Jehad Alshrafi)

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Displaced Palestinians, carrying their belongings traveling from Beit Hanoun to Jabaliya, a day after Israel's renewed offensive in the Gaza Strip, Wednesday, March 19, 2025. (AP Photo/Jehad Alshrafi)

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An injured United Nations Mine Action Service (UNMAS) worker is brought into al-Aqsa Martyrs Hospital following what the U.N. described as a strike in which an explosive ordnance was "dropped or fired" in Deir al-Balah, central Gaza, Wednesday, March 19, 2025. (AP Photo/Abdel Kareem Hana)

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The impact of a projectile is visible on the wall of the U.N. guesthouse, where United Nations workers were located when the building was struck, leaving one staff member dead and five others injured in Deir al-Balah, central Gaza, Wednesday, March 19, 2025. (AP Photo/Abdel Kareem Hana)

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An injured United Nations Mine Action Service (UNMAS) worker is taken into the al-Aqsa Martyrs hospital after an explosion in Deir al-Balah in central Gaza, Wednesday March 19, 2025.(AP Photo/Abdel Kareem Hana)

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An injured United Nations Mine Action Service (UNMAS) worker is treated at the al-Aqsa Martyrs hospital after an explosion in Deir al-Balah in central Gaza, Wednesday March 19, 2025.(AP Photo/Abdel Kareem Hana)

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EDS NOTE: GRAPHIC CONTENT - EDS NOTE GRAPHIC CONTENT.-Palestinians evacuate an injured man after his house was hit by an Israeli bombardment in Gaza City, Wednesday, March 19, 2025. (AP Photo/Jehad Alshrafi)

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Palestinians evacuate an injured man after his house was hit by an Israeli bombardment in Gaza City, Wednesday, March 19, 2025. (AP Photo/Jehad Alshrafi)

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Palestinians evacuate an injured man after his house was hit by an Israeli bombardment in Gaza City, Wednesday, March 19, 2025. (AP Photo/Jehad Alshrafi)

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An injured United Nations Mine Action Service (UNMAS) worker is taken into the al-Aqsa Martyrs hospital after an explosion in Deir al-Balah in central Gaza, Wednesday March 19, 2025.(AP Photo/Abdel Kareem Hana)

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Palestinians inspect their damaged house following an Israeli bombardment in Deir al-Balah, Gaza Strip on Wednesday, March 19, 2025. (AP Photo/Abdel Kareem Hana)

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Mourners pray over the bodies of Palestinians killed in the Israeli bombardment of the Gaza Strip as they are brought for burial at Al-Aqsa Hospital in Deir al-Balah, Wednesday, March 19, 2025. (AP Photo/Abdel Kareem Hana)

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Israelis march in a protest against Prime Minister Benjamin Netanyahu and his plans to dismiss the head of the Shin Bet internal security service, in Jerusalem on Wednesday, March 19, 2025. (AP Photo/Ohad Zwigenberg)

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Israelis march on a highway toward Jerusalem to protest Prime Minister Benjamin Netanyahu's plans to dismiss the head of the Shin Bet internal security service, on Wednesday, March 19, 2025. (AP Photo/Ohad Zwigenberg)

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