Israel says these photos show how Hamas places weapons in and near U.N. facilities in Gaza, including schools-InfoExpress

United Nations — Israel has accused the Palestinian militant group Hamas of committing "double war crimes" by not only firing rockets at civilians, but firing them from and near United Nations-run facilities in the Gaza Strip that should be "out of bounds" — and at least one senior U.N. official who spoke with CBS News agrees.

Hamas' use of civilians as human shields in Gaza was confirmed during the last major conflict in 2014, but its use of U.N. facilities to house and launch weapons has increased over the last eight years, putting U.N. staff and other civilians at greater risk, Israeli officials say.

U.N. officials told CBS News on Wednesday that 99 members of their staff have been killed in Gaza since the Palestinian enclave's Hamas rulers triggered the current war with their brutal Oct. 7 terror attack. UNRWA, the U.N.'s Palestinian refugee relief agency, says it has more than 13,000 staff in Gaza running schools, health clinics and other services.

Israel Defense Forces spokesman Lt. Col. Jonathan Conricus told CBS News that Israel's forces have seen "a systemic abuse by Hamas of sites and locations that are supposed to enjoy special protection under the Geneva Convention and humanitarian law," including not only U.N. facilities, but other schools, clinics, mosques, churches and hospitals.

U.N. facilities are "supposed to be out of bounds, according to the law of armed conflict, and specially protected," Conricus said, calling Hamas' use of U.N. locations "a double war crime."

IDF says photos show Hamas rockets at U.N. facilities

The IDF shared three recent photos with CBS News, including one that it said showed a Hamas rocket launching site positioned in a UNRWA warehouse facility in southern Gaza, and another very close to an UNRWA-run school.

Israel Defense Forces officials say this photo shows a Hamas rocket launch site located in a diplomatic building near a U.N. school in Gaza. Israel Defense Forces photo

As Israel moves into the sites during its ground operations in Gaza, it is sharing photos and video of what it says it has found. This week, Conricus said, it found "Boy Scout camps that have rocket launchers in them, rocket launchers next to children's playgrounds, rocket launchers and ammunition and military facilities within school compounds, and the false systematic abuse of hospitals and ambulances by Hamas."

Israel Defense Forces officials say this photo shows a Hamas rocket launch site located inside a U.N. building in Gaza. Israel Defense Forces photo

Hamas also takes advantage of its extensive network of tunnels running under Gaza neighborhoods.

"Instead of building schools and roads and hospitals and proper housing for civilians, which is what the international aid is intended for, Hamas has taken that cement and construction material and the money and the resources and built a city underneath the city, with hundreds of miles — and I'm not exaggerating — hundreds of miles of tunnels underneath the city," U.S. alternate Ambassador to the U.N. Robert Wood told a U.N. committee on Tuesday.

"Palestinian civilians are not to blame for Hamas's atrocities or for the grave humanitarian crisis in Gaza. They are its victims," U.S. Secretary of State Antony Blinken wrote this week.

Israel says Hamas' use of U.N. facilities has "expanded over the years"

Hamas' use of U.N. buildings for its weapons and fighters is not new. During the group's last major war with Israel, between 2012 and 2014, a U.N. inquiry found weapons had been placed inside an UNRWA school in the Hamas-run Gaza Strip and that it was highly likely that an unidentified Palestinian armed group could have used the school premises to launch attacks.

In the same 2015 report, then-Secretary-General Ban Ki-moon said that he was "dismayed that Palestinian militant groups would put United Nations schools at risk by using them to hide their arms."

UNRWA, the U.N. agency that supports Palestinians across the region, said at the time that it "strongly and unequivocally condemns the group or groups responsible for this flagrant violation of the inviolability of its premises under international law," adding that "especially during escalations of violence, the sanctity and integrity of U.N. installations must be respected."

Juliette Touma, director of communications for UNRWA, told CBS News on Wednesday, "We are committed to stay in Gaza and to continue to deliver humanitarian assistance to people who need us most, but we are facing significant challenges. … We hope to have more assistance coming in, we hope to have the siege lifted, we hope to have a humanitarian cease-fire as soon as possible."

Asked about the IDF photos, Touma said she did not have specific information on weapons in or near facilities, but said, "What I can confirm is that UNRWA does inspections of all of its facilities across the Gaza Strip. And towards the end of September we had done an inspection of all of our U.N. facilities across the Gaza Strip, and this inspection was complete."

Touma said UNRWA shares the coordinates of all their facilities every day with the parties, including "with Israel and the de-facto authorities," meaning Hamas.

But on Wednesday, in a sign of increased tension between the U.N. and Hamas, Salama Maruf, head of the media bureau of Hamas, accused UNRWA of "colluding" with Israel in the "forced displacement" of residents of Gaza, the AFP news agency reported. "UNRWA and its officials bear responsibility for this humanitarian catastrophe, in particular the residents of the Gaza (City) area and north of it" who are following instructions to evacuate, Maruf said.

U.N. spokesperson Stephane Dujarric disputed that claim, telling reporters at U.N. headquarters on Wednesday, "UNRWA, and the U.N. in general, doesn't collude with anyone. Our only focus, and UNRWA's only focus, is to support the civilian population in Gaza in what is a horrendous and indescribable moment in their history, and we will continue to do that."

The IDF says it's no mystery who's putting weapons in U.N. schools, and that Hamas is doing it now more than ever.

"According to our intelligence, not only is it happening but it has been expanded over the years, tunnels underneath U.N. facilities, rocket launchers next to or very — just within the compounds of U.N. facilities, and the general endangering of U.N. staff and U.N. facilities by Hamas, systematically," Conricus told CBS News.

He added that "the greatest shortcoming is the fact that we don't hear clear, unequivocal statements by the leaders at the U.N. calling out Hamas for what they're doing… endangering the lives of U.N. personnel."

A precarious balance for the U.N. in Gaza

"Hamas and other militants use civilians as human shields and continue to launch rockets indiscriminately towards Israel," U.N. Secretary-General Antonio Guterres said this week.

U.N. officials have been reluctant, however, to speak about Hamas' use of schools or other facilities run by U.N. agencies in Gaza.

"It would put our staff in jeopardy to call out Hamas for use of our buildings or schools," a U.N. official told CBS News, speaking on condition that he remain anonymous.

He said the U.N. was not aware of any weapons being hidden at its facilities, just as it was unaware of the same practice in Gaza before it carried out its inquiry after the last conflict in 2015, and he added an observation to highlight the difficulties for a humanitarian agency in trying to detect items that have been deliberately hidden.

"If the Israelis, with all their intelligence capabilities, did not know an attack was going to happen, how can we know that weapons are hidden under or near the U.N. in Gaza?"

The official added, "Right now we are in the middle of a humanitarian disaster and the only priority is the safety of our 13,000 staff and getting aid in, particularly with 99 U.N. staff already killed in the conflict."

A second senior U.N. official, who also spoke on the condition of anonymity to discuss the sensitive topic, told CBS News: "Of course, we assume that Hamas is using U.N. facilities in one way or another; it uses mosques, hospitals, schools, and those all should have extra protection status under international law."

The U.S. and Israel have been in agreement on many of the issues related to the current conflict, but on Wednesday, statements differed. Israel's Prime Minister Benjamin Netanyahu said Israel will have "security responsibility" in Gaza after the war, while senior U.S. officials called for a Palestinian-led future.

These differences were again apparent on Israeli intelligence. Asked about the pictures that the IDF provided, one U.S. official told CBS News that they've seen no information to suggest there are Hamas rockets at U.N. facilities. But another U.S. official said, "Hamas has been known to store weapons at U.N. facilities, endangering U.N. staff."

One of the senior U.N. officials noted that Hamas remains, for the time being, the de-facto authority in Gaza, and they both said U.N. agencies should try to protect their staff while continuing to carry out their missions to help civilians caught up in the war.

–CBS News' Eleanor Watson contributed reporting.