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

The Houthis have already detained U.N. staffers, as well as individuals associated with the once-open U.S. Embassy in Sanaa, Yemen’s capital, and aid groups.

“Yesterday, the de facto authorities in Sanaa detained additional U.N. personnel working in areas under their control,” the U.N. statement read. “To ensure the security and safety of all its staff, the United Nations has suspended all official movements into and within areas under the de facto authorities’ control.”

Before Friday, the U.N. had a total of 16 Yemeni staff in Houthi detention. Staffers found seven others had been taken and halted their work, which provides food, medicine and other aid to the impoverished nation.

In June, the U.N. acknowledged 11 Yemeni employees were detained by the Houthis under unclear circumstances as the rebels increasingly cracked down on areas under their control. Several dozen others from aid agencies and other organizations are also held.

The Houthis have held Yemen’s capital since 2014. The Iranian-backed rebels have been at war with a Saudi-led coalition battling on behalf of the country’s exiled government since 2015.