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.

The United Nations said on Friday that Yemen's Houthi rebels have once again detained its personnel in the war-wracked country. They were detained in areas controlled by the Iran-backed militia, the UN Yemen office said.