NEW YORK CITY: The death of a Yemeni UN employee who had been detained by the Houthis for more than two years raised “serious concerns about possible ill-treatment,” the organization said on Thursday, warning that it could amount to a serious violation of international law.

Mohammed El-Shami, who worked for the UN Human Rights Office, was the second member of UN staff to die while arbitrarily detained by the Iran-backed Houthi militia in Yemen.

UN spokesperson Stephane Dujarric said on Thursday the circumstances of his death, including a “prolonged failure” to disclose reliable information about his fate, warranted a thorough investigation.

“Such acts, if established, may constitute serious violations of applicable international law, including international human rights law,” he told reporters.

El-Shami had been detained by the Houthis since June 6, 2024, and the Houthis provided no information about his well-being during that time, despite repeated UN requests. His family was informed of his death about a week ago but they believe he died more than a month before that. A Yemeni government minister alleged El-Shami was tortured to death in a Houthi prison.

Dujarric on Thursday renewed UN calls for a prompt, independent, impartial and transparent investigation into the case to establish the precise date, cause and circumstances of his death, the conditions of his detention, and whether he received adequate and timely medical care. It must also explain why his family and the UN were not promptly informed that he had died, identify those responsible and hold them to account, he added.

The death raised “grave concerns” about the well-being of other UN and humanitarian workers who remain in Houthi custody, Dujarric said, “particularly those with serious medical conditions.”

He urged the Houthis to immediately provide verifiable information on the whereabouts and health of all detainees, allow regular contact with their families, and ensure they have access to medical care, including specialized treatment.

The UN also demanded it be granted access to all detainees to assess their medical conditions, and repeated its call for the release of all detained UN personnel, starting with those in need of critical medical treatment.

The first member of UN staff to die in Houthi detention was a World Food Programme employee in February 2025. The UN said 70 of its employees, five former members of staff, and a number of workers from humanitarian and civil society groups remain in Houthi detention. The militia accuses the detainees of spying for the US and Israel. The UN rejects the charges, which carry the death penalty in Yemen.

As the detentions continue, the humanitarian crisis in Yemen is deepening. The UN’s Office for the Coordination of Humanitarian Affairs said nearly 310,000 people have been forced from their homes since the beginning of August, with civilians fleeing in several governorates. Nearly 135,000 of them, more than 40 percent of all those recently displaced, were in Taiz Governorate.

The International Committee of the Red Cross on Wednesday delivered four trucks of medical supplies, including surgical kits, to hospitals in the city of Taiz, which is under siege by the Houthis, to treat the wounded and support health facilities that are under severe strain.

Dujarric said a road into the city had only been reopened following lengthy negotiations and did not mean the Houthis had lifted their siege.

The World Food Programme and its partners have launched an emergency meals initiative in the city, using locally sourced ingredients, initially targeting 2,000 vulnerable families in three districts.

Shelter needs among the displaced also far outstrip available supplies. Aid organizations have provided emergency shelter for about 5,600 families, which is only a little over 10 percent of the more than 51,000 who have been displaced since August. Tents and shelter kits for another 4,600 families were due to arrive soon.