Thousands of workers from Gaza, who were employed in Israel when the war started, have gone missing since then amid a campaign of mass arrests.

Human rights groups and trade unions believe some of the workers have been illegally detained in military facilities in the occupied West Bank, following the revocation of their permits to work in Israel. Authorities in Israel have so far refused to release the names of those they are holding.

When the Palestinian armed group, Hamas, launched an unprecedented assault on the south of Israel on October 7, about 18,500 residents of Gaza held permits to work outside the besieged strip. The exact number of workers present in Israel as hostilities began remains unknown, but thousands are thought to have been rounded up by the Israeli army and transferred to undisclosed locations.

Walid*, a Palestinian worker born in Gaza, had lived in the occupied West Bank for more than 25 years when Israel launched its relentless bombardment of Gaza which has so far killed more than 7,000 people and has lasted for three weeks. On October 8, he was arrested as he headed for work and detained in a facility in the Almon area, also known as Anatot, built on the ruins of the Palestinian town of Anata that Israel confiscated in occupied East Jerusalem.

The facility, human rights organisations say, is among those repurposed by the Israeli government to hold hundreds of workers in arbitrary detention, in breach of international law.

Walid, whose real name and personal details are being withheld to avoid reprisals, described being kept in a “cage” without a roof, under the sun and without food, water or access to the toilet for three days, according to a written testimony given to the Israel-based human rights organisation HaMoked and seen by Al Jazeera.

He was then moved to an area of about 300 square metres where hundreds of labourers shared a chemical toilet cubicle. When he asked to contact the Red Cross, he was cursed and beaten up by soldiers.

Walid was released after Israeli officers ascertained that, although he was born in Gaza, he is a resident of the West Bank. His testimony is among the few accounts to have so far emerged from the detention centres where Gaza workers have been held incommunicado and without legal representation since October 7.

Not clear ‘where, how many, under what legal status’

“We have been receiving hundreds and hundreds of phone calls from family members of people who were working in Israel prior to the [October 7] attacks,” Jessica Montell, executive director of HaMoked, told Al Jazeera.

So far, Montell says, more than 400 families and friends of missing people have got in touch with the organisation, trying to trace their loved ones as they simultaneously struggle to survive Israel’s bombardments and “total” siege. Those calls have been dwindling in the past week as residents of Gaza are increasingly cut off from communications.

As part of its work, HaMoked regularly submits the names of detainees to the Israeli authorities to find out where they may be held.

“The Israeli military is supposed to inform us within 24 hours of who they are holding, which location they are being held in,” Montell said. “But for all those Gazans, they told us [they]’re not the right [authority to] address.”

“It can’t be the case that it’s not clear where they’re being held, how many are being held, under what conditions, under what legal status,” she added.

A group of six local organisations, including HaMoked, have petitioned Israel’s High Court to disclose the names and locations of the detainees and to ensure humane holding conditions.

According to the petitioners, some of the Palestinians have been detained in the Almon area – where Walid was detained – as well as in Ofer, near Ramallah, and in Sde Teyman, near Beer al-Sabe (Be’er Sheva), in the southern Naqab or Negev desert.

Once the hostilities began and the Beit Hanoun crossing (known as Erez to Israelis) into northern Gaza was shut, workers attempted to make their way to the West Bank to find shelter among Palestinian residents.

But on October 10, Israel’s Coordinator of Government Activities in the Territories (COGAT) revoked all work permits it had previously issued to Gaza residents, instantly turning permit-holders into “illegal aliens”.

Al Jazeera contacted the Israeli army, as well as COGAT, the body that controls the permit system in the occupied territories. Both declined to comment or provide further information on the number of workers whose permits were revoked, as well as how many have been imprisoned and on what grounds.

‘Unparalleled’

Miriam Marmur, advocacy director of Gisha, an Israeli human rights organisation which calls for the freedom of movement of Palestinians, said the situation was “unparalleled”.

“Of course, at any given point, there are thousands of Palestinians that are being held in administrative detention by Israel,” she told Al Jazeera. “But these are the first Palestinians to be held en masse. The nature of their detention, the revocation of people’s permits and the fact that Israel is so far refusing to divulge any information about where they are … that is not something I have seen before,” she said.

Marmur added that the arrests were “illegal and appear to be acts of vengeance which stand in violation of international law”.

Hamas seized at least 224 people as hostages as it waged its attack on southern Israel on October 7, according to Israeli officials. Four have since been released.

According to Walid’s testimony, one of the officers at a detention camp told detainees there would be no chance of them being released as long as there were Israeli hostages in Gaza.

“This isn’t an official statement, but certainly it’s an indication that, at least to some of the people involved in this, there is a kind of desire to use these workers as bargaining chips,” Marmur said.

Under Israel’s permit system, very few Palestinians from the Gaza Strip can leave the territory, as all border crossings have been under Israeli or Egyptian control since Hamas took power in 2007.

Permits can be issued for work, health and humanitarian reasons after careful vetting by the Israeli authorities. Most of the workers from Gaza – where the overall unemployment rate is 45 percent and youth unemployment has soared to 70 percent – take up manual jobs in Israel, where the pay is several times higher.

Human rights groups are concerned about further arrests amid continuing raids in the West Bank, including in areas nominally under the full control of the Palestinian Authority.

“We never had a situation like that, where people are trapped and can’t go home, and are put in a sort of camp,” said Hassan Jabareen, the director of Adalah, the legal centre for Arab minority rights in Israel. “These were just workers. The only comparison is perhaps with [undocumented] refugees.”

Mass arrests

The Minister of Labour for the Palestinian Authority estimated that about 4,500 workers are unaccounted for and are believed to have been detained by Israeli forces. Israeli media outlet N12 reported that 4,000 Palestinians from Gaza were being interrogated in Israeli holding facilities over their possible involvement in the attack.

Alongside Gaza workers, Israeli forces have detained more than 1,450 Palestinian residents of the West Bank since October 7, according to estimates by the Palestinian Prisoners Society.

The arrests have taken place against a backdrop of laws and amendments that human rights organisations say amount to punitive measures.

On October 18, the Israeli parliament, known as the Knesset, approved a temporary plan that strips Palestinian prisoners of the right to at least 4.5 square metres of space, enabling cells that used to hold five people to hold more than twice as many.

According to Physicians for Human Rights Israel (PHRI), authorities also disconnected access to power and water supplies, limited the number of meals per day, restricted prisoners to their cells and prevented access to medical clinics and visits by legal representatives and other officials. At least two prisoners have died while in custody since the beginning of the latest round of hostilities.

“We are calling on the Israeli authorities to abide by international law and allow food, water and visitations,” Naji Abbas, case manager at PHRI, told Al Jazeera. “And to stop taking revenge on Palestinian prisoners.”