ADEN, Yemen, Dec. 18 (Xinhua) -- Yemen's Houthi group on Thursday detained four Yemeni staff members of United Nations agencies in the capital Sanaa, a UN source said.

Speaking on condition of anonymity, the source said that the detained employees work for the United Nations Department of Safety and Security, the United Nations Development Program and the United Nations Children's Fund.

According to the source, Houthi security forces raided their residences in Sanaa before taking them into custody.

A local security source told Xinhua that the arrests are part of "a renewed campaign" by the Houthi intelligence forces targeting Yemeni nationals employed by the United Nations in Sanaa. The source added that the detentions could "expand beyond the capital to other areas controlled by the group."

There was no immediate comment from the Houthi group regarding the incident. However, Houthi authorities have previously justified similar arrests by accusing UN staff and aid workers of collaborating with U.S. and Israeli intelligence agencies, allegations rejected by the United Nations.

The detentions came one day after UN Secretary-General Antonio Guterres condemned the continued arbitrary detention of UN personnel by the Houthi group in Yemen.

"I strongly condemn the continued arbitrary detention of 59 UN colleagues and partner personnel, as well as staff from NGOs, civil society organizations, and diplomatic missions," Guterres told reporters on Wednesday after briefing the UN Security Council on the situation in Yemen in closed-door consultations. "I call for their immediate and unconditional release, in accordance with international law," he said.

Guterres said that in recent days, Houthi de facto authorities had referred three UN personnel to a special criminal court over their performance of official UN duties, stressing that the referral must be rescinded and the charges dropped.

Dozens of UN staff and aid workers have been held by the Houthis since June 2024, despite repeated UN appeals for their release.

The Houthi group has controlled Sanaa and most of Yemen's northern provinces since late 2014. Despite the protracted conflict and ongoing detentions, several UN agencies and international organizations continue to operate in the capital. Enditem