The United Nations has suspended humanitarian operations in northern Saada after rebels detained eight more U.N. staffers, during one of the world's worst humanitarian crises.

The United Nations said on Tuesday that one of its staff members had died in detention in northern Yemen, where the U.N. has repeatedly called for the Houthi movement to free detained U.N. employees.

The United Nations announced the suspension of its activities in Yemen's Saada region, a Houthi stronghold, after the rebels detained multiple personnel there this year.