People inspect the site of Saudi-led airstrikes Sunday in Dhamar. (Stringer/Reuters/)

A Saudi-led coalition airstrike on a Yemeni prison has left more than 100 people “presumed killed,” said the Red Cross late Sunday after visiting the facility, disputing Saudi officials’ claims that the attack had struck a rebel arms depot.

In a statement carried on Saudi state television on Sunday, the Saudi-led coalition said it had destroyed a warehouse that the rebels, known as the Houthis, used to house drones and missiles. The Houthis maintained it was a detention center.

“Witnessing this massive damage, seeing the bodies lying among the rubble was a real shock,” said Franz Rauchenstein, the head of the International Committee of the Red Cross in Yemen. “People who are not taking active part in combat should not die in such a way.”

According to the group, also known as the ICRC, the multistory building that served as a detention facility collapsed from the airstrike. It held around 170 detainees, and 40 of them were being treated for injuries. “The rest are presumed killed, though no toll has been confirmed,” the ICRC said. 

The United Nations’ primary human rights office in Yemen said 52 detainees were among the dead, and that at least 68 detainees are missing

“Today’s event is a tragedy,” said Martin Griffiths, special envoy of the secretary-general on Yemen in a statement. “I hope the Coalition will launch an enquiry into this incident. Accountability needs to prevail.”

The Saudi-led coalition did not immediately respond to the reports confirming the attack struck a detention facility. In a statement Sunday morning, the coalition insisted the compound was “a legitimate military target” with air defense equipment present.

The coalition said the facility was an illegal “secret prison” not placed an any no-strike list, adding that it would investigate the incident.

In the immediate aftermath of the attack, there were already fears that the airstrike had killed civilians.

“We are taking these reports extremely seriously,” Rauchenstein said in a tweet earlier on Sunday and before he and his team visited the area. “I am on my way to Dahmar #Yemen to assess the situation. We have visited detainees in this location before, as we do in other places as part of our work.”

 In a separate tweet, the Red Cross said it had dispatched a team carrying “urgent medical supplies that can treat up to 100 critically wounded persons.” It added that it would pick up 200 donated body bags along the way, “following air strikes which are reported to have killed or wounded dozens of detainees.”

The attack is the latest by the Saudi-led coalition to target civilians in Yemen. Air assaults have in the past struck hospitals, health clinics, markets, even school buses. The coalition has said it has taken measures to prevent civilian casualties, but human rights groups and the United Nations say it continues to break international law.

The coalition has launched airstrikes on Houthi detention facilities in previous years. An October 2016 attack on a prison in the western port city of Hodeida killed more than 60 people.

The coalition, made up Sunni Muslim countries, has been battling the Shiite Houthis since March 2015 in an effort to restore Yemen’s internationally recognized government and prevent Iran from gaining influence through its alliance with the Houthis.

In recent months, the Houthis have shown greater military capability, targeting Saudi airports and oil fields with armed drones and missiles. The coalition has responded with airstrikes.

As many as 95,000 people, including tens of thousands of civilians, have been killed by violence since the war began, according to the Armed Conflict Location and Event Data Project, a nongovernmental organization tracking war casualties in Yemen.

On Sunday, Yemen Red Crescent volunteers removed bodies from the rubble with the help of bulldozers and other heavy machinery, the ICRC said, adding that it would take several days to find all the corpses.

“These detainees shall not be and are not forgotten,” said Fabrizio Carboni, the ICRC’s regional director for the Middle East in a statement, urging Yemen’s warring parties to behave more responsibly when conducting military operations. 

“The conflict in Yemen is claiming too many civilian victims and others not taking part in hostilities,” he said.