The Israeli military has rounded up hundreds of Palestinians across the northern Gaza Strip, separating families and forcing men to strip to their underwear before trucking some to a detention camp on the beach, where they spent hours, in some cases days, subjected to hunger and cold, according to human rights activists, distraught relatives and released detainees themselves.

Palestinians detained in the shattered town of Beit Lahiya, the urban refugee camp of Jabaliya and neighborhoods of Gaza City said they were bound, blindfolded and bundled into the backs of trucks. Some said they were taken to the camp at an undisclosed location, nearly naked and with little water.

“We were treated like cattle, they even wrote numbers on our hands," said Ibrahim Lubbad, a 30-year-old computer engineer arrested in Beit Lahiya on Dec. 7 with a dozen other family members and held overnight. “We could feel their hatred.”

The roundups have laid bare an emerging tactic in Israel’s ground offensive in Gaza, experts say, as the military seeks to solidify control in evacuated areas in the north and collect intelligence about Hamas operations nearly 10 weeks after the group’s deadly Oct. 7 attack on southern Israel. Militants killed about 1,200 people and abducted over 240 that day.

“This is already helping us, and it will be crucial for the next stage of the war,” said Yaakov Amidror, a former national security adviser to Prime Minister Benjamin Netanyahu. “That’s the stage where we clean areas from all the remnants of Hamas.”

In response to questions about alleged mistreatment, the Israeli military said that detainees were “treated according to protocol” and were given enough food and water. The army spokesman, Rear Adm. Daniel Hagari, said this week that arrests took place in two Hamas strongholds in northern Gaza and that detainees were told to strip to make sure they didn't conceal explosives.

Hagari said the men are questioned and then told to dress, and that in cases where this didn't happen, the military would ensure it doesn't occur again. Those believed to have ties to Hamas are taken away for further interrogation, and dozens of Hamas members have been arrested so far, he said.

The others are released and told to head south, where Israel has told people to seek refuge, Hagari said.

Photos and video showing Palestinian men kneeling in the streets, heads bowed and hands bound behind their backs, sparked outrage after spreading on social media. U.S. State Department spokesman Matthew Miller on Monday said the United States “found those images deeply disturbing" and was seeking more information.

To Palestinians, it is a stinging indignity. Among those rounded up were boys as young as 12 and men as old as 70, and they included civilians who lived ordinary lives before the war, according to interviews with 15 families of detainees.

“My only crime is not having enough money to flee to the south,” said Abu Adnan al-Kahlout, an unemployed 45-year-old with diabetes and high blood pressure in Beit Lahiya. He was detained Dec. 8 and released after several hours when soldiers saw he was too faint and nauseated to be interrogated.

“Do you think Hamas are the ones waiting in their homes for the Israelis to come find them now?" he asked. “We stayed because we have nothing to do with Hamas.”

Israeli forces have detained at least 900 Palestinians in northern Gaza, estimated Rami Abdo, founder of the Geneva-based advocacy group Euro-Med Human Rights Monitor, which has worked to document the arrests. Based on testimony it collected, the group presumes Israel is holding most detainees from Gaza at the Zikim military base just north of the enclave.

Tens of thousands of Palestinians are believed to have stayed in the north despite the danger — unable to afford a ride, unable to abandon disabled relatives or convinced things are no safer in the overcrowded south, which also has come under daily bombardment.

Palestinians cowered with their families for days as Israel poured heavy machine-gun fire into Beit Lahiya and Jabaliya, the tank shelling and firefights with Hamas militants stranding families in their homes without electricity, running water, fuel or communications and internet service. Hundreds of buildings have been crushed by Israeli bulldozers, clearing paths for tanks and armored troop carriers.

“There are corpses all over the place, left out for three, four weeks because no one can reach them to bury them before the dogs eat them,” said Raji Sourani, a lawyer with the Palestinian Center for Human Rights in Gaza. He said he saw dozens of dead bodies as he made his way from Gaza City to the southern border with Egypt last week. Israeli forces are holding one of his colleagues, human rights researcher Ayman al-Kahlout, in custody.

Palestinians recount similar terrifying scenes as the Israeli military combs through northern towns. Soldiers go door to door with dogs, using loudspeakers to call on families to come outside, residents said. Or they blast doors of homes open with a grenade, yelling at men to remove their clothes and confiscating money, IDs and cellphones.

In most cases, women and children are told to walk away to find shelter.

Some released detainees reported soldiers shouting sexually explicit insults at women and children and beating men with their fists and rifle butts after bursting into their homes. Others reported enduring humiliating stretches of near-nudity as Israeli troops took the photos that later went viral. Some guessed they were driven several kilometers (miles) before being dumped in cold sand.

The Israeli military declined comment on where the detainees were taken.

Abu Adnan al-Kahlout's family believes its members were singled out for mistreatment because they share a last name with the spokesman for Hamas’ military wing better known by his nom de guerre, Abu Obeida. But family members — among them electricians, a tailor, a bureau chief for London-based news site Al-Araby Al-Jadeed and employees of Hamas' political rival, the Palestinian Authority — insist they have nothing to do with Gaza's Islamic militant rulers.

Three family members remain in Israeli custody. No one has heard from them in days. Other relatives, like 15-year-old Hamza al-Kahlout and 65-year-old Khalil al-Kahlout, returned home Dec. 8 to find their five-story building a charred skeleton. They fled to a nearby U.N. shelter at a school. But the Israeli military stormed the school and arrested them again as it pressed on with its crackdown.

Released detainees said their wrists were blistered from tightly drawn handcuffs. Exposed to the chill of night, they endured repeated questions about Hamas activities that most couldn't answer. Soldiers kicked sand in their faces and beat those who spoke out of turn.

Several Palestinians held for 24 hours or less said they had no food and were forced to share three 1.5-liter bottles with some 300 fellow detainees. Construction worker Nadir Zindah said he was fed meager scraps of bread over four days in custody.

Darwish al-Ghabrawi, a 58-year-old principal at a U.N. school, fainted from dehydration. Mahmoud al-Madhoun, a 33-year-old shopkeeper, said the only moment that gave him hope was when soldiers released his son, realizing he was just 12.

Returning home brought its own horrors. Israeli soldiers dropped detainees off after midnight without their clothes, phones or IDs near what appeared to be Gaza's northern border with Israel, those released said, ordering them to walk through a landscape of destruction, tanks stationed along the road and snipers perched on roofs.

“It was a death sentence,” said Hassan Abu Shadkh, whose brothers, 43-year-old Ramadan and 18-year-old Bashar, and his 38-year-old cousin, Naseem Abu Shadkh, walked shoeless over jagged mounds of debris until their feet bled. They begged the first person they saw for rags to cover their bodies.

Naseem, a farmer in Beit Lahiya, was shot and killed by an Israeli sniper as they made their way to a U.N. school in Beit Lahiya, Abu Shadkh said. His brothers were forced to leave their cousin's body in the middle of the road.

Israeli officials say they have reason to be suspicious of Palestinians remaining in northern Gaza, given that places like Jabaliya and Shijaiyah, in eastern Gaza City, are well-known Hamas bastions.

“We will continue to dismantle each and every one of these Hamas strongholds until we finish in Jabaliya and Shijaiyah and then continue,” government spokesperson Eylon Levy said, signaling the military would widen its campaign as ground forces press deeper into the south, where over a million Palestinians have taken refuge.

He said the southern town of Khan Younis, now at the center of fighting, would be next.

“We will of course work out who needs to be arrested and detained and put to justice as a Hamas terrorist and who does not," Levy said.

Human rights groups say mass arrests should be investigated.

“It isn’t clear on what basis Israel is holding them and it raises real serious questions,” said Omar Shakir, Human Rights Watch’s regional director. “Civilians must only be arrested for absolutely necessary and imperative reasons for security. It's a very high threshold."

Meanwhile, families plead for information about loved ones who disappeared. The International Committee of the Red Cross said its hotline had received 3,000 calls from people trying to connect with missing relatives from the beginning of the war until Nov. 29.

“I can't take not knowing, I feel sick," said 40-year-old Zindah, the construction worker, who arrived Monday by foot at the hospital in Deir al-Balah after four days in Israeli detention with his 14-year-old son, Mahmoud. “I don’t know where my wife and seven kids are. Are they alive? Are they dead? Are they in prison?”