The United Nations human rights chief on Friday called on Yemen's Houthi authorities to hand over the remains of a Yemeni UN staff member who died in their custody weeks earlier under unexplained circumstances.

Mohammed al-Shami had been detained by the Houthis since 6 June 2024. His family only learned of his death on 30 October, more than a month after it occurred, and has been given no account of how or why he died.

"Our colleague must be laid to rest in a dignified manner, in accordance with the wishes of his family - which was denied contact with him for two years while he was in detention," said Volker Turk, the UN high commissioner for human rights.

In a statement issued earlier this week, al-Shami's family said the Houthis had agreed in principle to an investigation into the death.

"Do not allow Mohammed to die twice: once when he was taken from his family and disappeared, and again when the truth about his fate is allowed to disappear from the world," the family's statement said.

The case comes as more than 70 UN employees and dozens of humanitarian workers remain held in Yemen, part of a prolonged detention campaign by the de facto authorities that has drawn repeated international condemnation.

Turk's office said a video circulating this week appeared to show one of the detained personnel "confessing", and raised concerns that the detainees could be facing torture or other ill-treatment.

In a post on social media, the UN Human Rights office said Turk was demanding that al-Shami's body be returned to his family without delay, and that the Houthis take urgent steps to establish the date, cause and circumstances of his death while ensuring those responsible are held accountable.

Turk also called for all detained UN and humanitarian personnel to be released immediately and unconditionally, saying the Houthi authorities must promptly provide information on the whereabouts and health of every person still in custody.