The United Nations said on Tuesday that one of its staff members had died in detention in northern Yemen, where the UN has repeatedly called for the Houthi movement to free detained UN employees.
The UN World Food Programme did not specify when or how its employee, who it said had been detained on January 23 with six others, had died.
UN Secretary-General Antonio Guterres condemned the death, calling for an immediate investigation and for those responsible to be held accountable.
"The circumstances surrounding this deplorable tragedy remain unclear, and the United Nations is urgently seeking explanations from the Houthi de facto authorities," he said in a statement.
The United Nations paused all operations in Yemen's Sa'ada region on Monday after more UN staff were detained by the Houthi authorities, deputy UN spokesperson Farhan Haq said.
"Heartbroken and outraged by the tragic loss of WFP team member, Ahmed, who lost his life while arbitrarily detained in Yemen. A devoted humanitarian and father of 2, he played a crucial role in our mission to deliver lifesaving food assistance," WFP Chief Cindy McCain said in a post on X.
The Houthis have controlled most populated parts of Yemen, including the capital Sanaa, since seizing power in 2014 and early 2015. Since 2021, the Houthis have detained dozens of UN staff. The group now has some 24 UN staff in detention.
"Their continued arbitrary detention is unacceptable. I renew my call for their immediate and unconditional release," Guterres said.
Yemen has been the focus of one of the world's largest humanitarian operations during a decade of civil war that disrupted food supplies. WFP says it provided assistance to 15.3 million people, or 47 per cent of the population, in 2023.