For years, the United Nations Relief and Works Agency sent millions of dollars each month to Gaza to pay employees and support hospitals, schools and other infrastructure, according to a new lawsuit. The money was wired from New York, where the agency has an office, to the West Bank, where financial institutions loaded some of that cash onto trucks to be driven across Israel to Gaza.

The suit, filed Monday in federal court in Manhattan, said some of those dollars ended up funding the military operations of Hamas, the Islamist group that has controlled Gaza for nearly 20 years and has pledged to erase the Jewish state. The money trail is at the heart of the case against seven current and former top UNRWA officials who are accused of knowing that Hamas siphoned off more than $1 billion from the agency to pay for, among other things, tunneling equipment and weapons that aided its attack on Israel on Oct. 7.

About 100 Israeli plaintiffs — including at least one who was held hostage by Hamas in Gaza, others who survived the attack, as well as the estates of some who died — are seeking unspecified financial damages. They claim that UNRWA is liable because it helped fund Hamas, which the United States and other countries deem a terrorist organization.

UNRWA has been sued several times since the attacks, with some cases claiming that the agency has abetted Hamas and others attempting to cut off UNRWA’s funding. The case filed on Monday goes further, describing how the plaintiffs believe agency money ended up in the hands of Hamas and how the terrorists used its resources in the attack on Israel.

The suit says that in Gaza, unlike other places the agency operates, UNRWA pays its 13,000 local employees in U.S. dollars that must be changed into shekels, the Israeli currency that is used in Gaza, by Hamas-affiliated money-changers who take a cut for the organization.

The civil suit faces many hurdles, particularly the question of whether a treaty affords the U.N. officials immunity. But if the case proceeds, it could allow other victims of Hamas attacks to seek damages from the U.N. Even if it fails, the suit could pressure nations donating money to UNRWA to reassess their support.

“Hamas did not carry out these atrocities without assistance,” the complaint says. It was “aided and abetted” by senior agency officials who for over a decade financed Hamas’s “terror infrastructure” and knew that they were “providing Hamas with the U.S. dollars in cash that it needed to pay smugglers for weapons, explosives, and other terror materiel.”

Juliette Touma, a spokeswoman for the agency, said Monday that it knew of the suit, but “has not been served with any legal process” She added: “The United Nations, including UNRWA, enjoys immunity from legal process, as do United Nations officials, including those serving with UNRWA.”

A senior Hamas official didn’t immediately respond to a request for comment.

Hamas does not have access to the global banking architecture that allows easy transfer of money across borders. For many years, Israel has allowed outside funds, including money from UNRWA, to be sent to Gaza to pay for basic necessities. The Israeli government facilitated a yearslong effort by the Qataris to send cash for humanitarian operations. But there have been widespread questions as to whether the Qatari money has been diverted by Hamas to pay for military operations.

UNRWA was created in 1949 and is funded primarily through donations from U.N. member nations. The United States has long been the largest contributor, giving $371 million in 2023, nearly 30 percent of the agency’s contributions, according to a congressional report.

The defendants named in the suit are Philippe Lazzarini, commissioner-general of UNRWA; Pierre Krähenbühl, the agency’s former head, who is now at the International Red Cross; Leni Stenseth, Sandra Mitchell and Margot Ellis, who are former deputy commissioners-general; Greta Gunnarsdottir, director of the agency’s office in New York; and Filippo Grandi, the U.N. high commissioner for refugees.

A spokeswoman for Ms. Stenseth declined to comment on the suit, and a spokesman for Mr. Grandi referred all questions to the U.N. secretary general’s office. Efforts to reach the other defendants were not immediately successful.

In an opinion essay written for The New York Times last month, Mr. Lazzarini distinguished acts of individuals from the work of the agency and said allegations that UNRWA or other U.N. organizations were engaged in terrorism “will further diminish our tools for peace and defense against inhumanity around the world.”

Under a treaty between the United States and United Nations, the four highest levels of U.N. officials have full diplomatic immunity, according to Larry Johnson, former deputy legal counsel at the U.N. Lower-level officials have “functional immunity,” which means they cannot be sued for actions taken as part of their jobs.

“We do not believe UNRWA has immunity for aiding and abetting” the attacks on Israel, Gavi Mairone, a human rights lawyer representing the plaintiffs, said in a statement.

The plaintiffs’ lawyers argue that the UNRWA officials can be sued in U.S. court because the agency has a New York office, raised funds in New York and used banks based in New York. The lawyers also said the Alien Tort Statutes allow non-Americans to sue in U.S. federal court for injuries suffered as a result of a violation of international laws.

The suit relies on a long and tortuous trail of cash that stretches from Manhattan to the Middle East.

According to the complaint, the agency each month would ask JPMorgan Chase to wire million of dollars to the New York branch of Arab Bank, which has its headquarters in Jordan and is one of the region’s largest financial institutions. The Arab Bank then transmitted the money to its branch in Ramallah, in the West Bank.

There, the money earmarked for UNRWA operations in Gaza was transferred to the Bank of Palestine in Ramallah and then withdrawn as U.S. dollars in cash, loaded onto trucks and driven across Israel to Gaza.

JPMorgan Chase declined to comment. Arab Bank and the Bank of Palestine did not respond to requests to speak about the case.

The suit argues that if UNRWA paid its Gaza staff in shekels, the money could be sent electronically, reducing the need to pay fees to Hamas-affiliated money changers. “Only Hamas benefits from UNRWA’s current cash-handling practices,” according to the complaint.

The complaint says the group used the money “to buy via smugglers its weapons, ammunition, explosives, construction materials for the tunnels and rocket-making supplies.”

The plaintiffs’ lawyers said the sources they used to establish details of the money trail included U.N. audits of UNRWA’s finances and an U.N. investigation of the agency, as well as press reports that include comments from UNRWA about the movement of money from New York into Gaza and the allocation of those funds.

The complaint does not reveal what evidence the plaintiffs will present to prove with certainty that UNRWA money in Gaza was used to finance the Oct. 7 attack. Nor does the complaint provide specific details to support the claim that Hamas controls the currency exchanges.

But a report by Key Aid Consulting for UNRWA in 2018 said that the exchanges are open to “leakage,” which includes “misappropriation, fraud, corruption, double-counting and any irregularity considered as a diversion of cash grants or vouchers from legitimate uses.”

Monday’s suit claims that whether the officials knew specifically about the Oct. 7 attacks is irrelevant, because they knew that “Hamas openly proclaimed its goal to target and murder innocent civilians” and knew that any support would help.

UNRWA has long been accused of having links to Hamas. In January, Israel accused a dozen agency employees of playing a role in the attacks on Oct. 7 or in their aftermath. The U.N. said that it had fired several employees after being briefed on the allegations. The accusations prompted eight countries, including the United States, to suspend some aid to UNRWA.

In April, an independent review commissioned by the United Nations said that Israel had not provided evidence that many of UNRWA’s thousands of employees are members of terrorist organizations. That prompted several nations to begin making donations again.