The United Nations on Friday suspended all travel into areas held by Yemen’s Houthi rebels after more of their staff were detained by the rebels.

All official movement of U.N. staff into or within Houth-held areas had been suspended to protect the safety of staff. The U.N. was actively engaging with senior Houthi representatives to demand the immediate and unconditional release of all its detained personnel and partners.

Yemen's Huthi rebels have detained another group of UN personnel, a United Nations statement said on Friday, after 13 staff were held last June.