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.

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 were trying to get a headcount across the U.N. agencies working in the country and had 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 U.N. added that it was “actively engaging with senior representatives” of the Houthis, who 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.

The Houthis did not immediately acknowledge the U.N.’s decision, which came as they have otherwise been trying to deescalate their attacks on shipping and Israel after a ceasefire was reached in the Israel-Hamas war.

U.S. President Donald Trump separately has moved to reinstate a terrorism designation he made on the group late in his first term that had been revoked by President Joe Biden , potentially setting the stage for new tensions with the rebels. It wasn’t clear if the Houthis viewed the U.N. detentions as being linked to the decision.

The Houthis earlier this week said they would limit their attacks on ships in the Red Sea corridor and released the 25-member crew of the Galaxy Leader , a ship they seized back in November 2023.

However, the Houthis have run a campaign targeting those with Western ties for some time.

The group has been airing repeated programs on television channels they control parading people they describe as working with Western intelligence agencies or the Israelis.

The war in Yemen has killed more than 150,000 people, including fighters and civilians, and created one of the world’s worst humanitarian disasters, killing tens of thousands more.

The Houthis’ attacks on shipping during the Israel-Hamas war have helped deflect attention from their problems at home. But they have faced casualties and damage from U.S.-led airstrikes targeting the group for months now, as well as other strikes by Israel.

Thousands have been imprisoned by the Houthis during the war. An AP investigation found some detainees were scorched with acid, forced to hang from their wrists for weeks at a time or were beaten with batons. Meanwhile, the Houthis have employed child soldiers and indiscriminately laid mines in the conflict.