UNITED NATIONS / SANAA / ADEN - UN Secretary-General Antonio Guterres said on Sunday that he strongly condemned the arbitrary detentions of at least 11 UN personnel by the Houthi de facto authorities in Yemen in areas under their control earlier in the day.

In a statement, the UN chief said he further condemned the forced entry into the premises of the World Food Programme, the seizure of UN property, and attempts to enter other UN premises in Sanaa.

Guterres said he strongly reiterated his demand for the immediate and unconditional release of those detained on Sunday, as well as all other personnel from the United Nations, international and national non-governmental organizations, civil society and diplomatic missions who have been arbitrarily detained since June 2024 and those held since 2021 and 2023.

"The continued arbitrary detention of all such persons is intolerable," he said.

He emphasized that the personnel of the United Nations and its partners must never be targeted, arrested or detained while carrying out their duties for the world body, adding that the safety and security of UN personnel and property as well as the inviolability of UN premises must be guaranteed at all times.

"The United Nations will continue to work tirelessly to secure the safe and immediate release of all arbitrarily detained individuals. The United Nations and its partners will continue to support the people of Yemen and their aspirations for a just and lasting peace," the UN chief said.

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At least 11 UN staff members were detained on Sunday in Sanaa and Hodeidah, bringing the total number of detained UN staff in northern Yemen to 34, according to UN Special Envoy to Yemen Hans Grundberg.

The Houthis said on Saturday that Ahmed al-Rahawi, prime minister of the Houthi-backed government, and several other ministers were killed in Israeli airstrikes on Sanaa on Thursday while attending a government workshop. The group vowed to retaliate, with Mahdi al-Mashat, head of the Supreme Political Council -- the Houthis' top governing body -- warning in a speech aired by Houthi-run al-Masirah TV that "Israel should await dark days." 

UN envoy urges de-escalation

UN Special Envoy to Yemen Hans Grundberg on Sunday urged de-escalation in Yemen as tensions rose between the Houthi group and Israel after Prime Minister Ahmed al-Rahawi of the Houthi-backed government was killed in Israeli airstrikes on Thursday.

"Yemen cannot afford to become a battleground for a broader geopolitical conflict," Grundberg said in a statement.

"These attacks need to stop," he said, urging all parties to "use available diplomatic channels to de-escalate" and to "protect civilians and civilian infrastructure in line with their obligations under international law."

The Houthis said on Saturday that al-Rahawi and several other ministers were killed in Israeli airstrikes on Sanaa on Thursday while they were attending a government workshop. The group vowed to retaliate, with Mahdi al-Mashat, head of the Supreme Political Council -- the Houthis' top governing body -- warning in a speech aired by Houthi-run al-Masirah TV that "Israel should await dark days."

The Houthis seized Sanaa in 2014, forcing the internationally recognized Yemeni government into exile in Aden. Since then, they have controlled much of northern Yemen, including Sanaa and Hodeidah, and set up an unrecognized government in the capital.

On Sunday, Israeli Prime Minister Benjamin Netanyahu told a weekly cabinet meeting that Israel would eliminate all Houthi leaders.

In a separate development, Grundberg condemned what he called a "new wave" of arbitrary detentions of UN personnel by the Houthis.

At least 11 UN staff members were detained on Sunday in Sanaa and Hodeidah, bringing the total number of detained UN staff in northern Yemen to 34, he said.

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Grundberg urged the Houthis to "immediately and unconditionally" release the detainees, warning that the continued detention of UN staff, aid workers, and civil society activists was undermining humanitarian operations and efforts to advance peace in Yemen.

Several employees of the UN World Food Program (WFP) were also arrested by the Houthis in Sanaa on Sunday, security and humanitarian sources told Xinhua.

A local security official, speaking on condition of anonymity, said one WFP employee was taken from the organization's headquarters in Sanaa, while several others were arrested from its office in Hodeidah. A WFP source in Yemen confirmed the arrests, adding that three security guards working at the Sanaa headquarters were also detained when Houthi forces stormed the building.

There has been no immediate comment from the Houthis regarding Sunday's arrests.

WFP staff arrested: sources

Several employees of the United Nations World Food Program (WFP) were arrested by the Houthi group in the Yemeni capital Sanaa on Sunday, security and humanitarian sources told Xinhua.

According to a local security official, who asked to remain anonymous, one WFP employee was taken into custody from the organization's headquarters in Sanaa, while several others were arrested from its office in the Red Sea port city of Hodeidah.

A WFP source in Yemen confirmed the arrests, adding that three security guards working at the Sanaa headquarters were also detained when Houthi forces stormed the building.

"We do not know the fate of the employees who were still inside the office during the raid," the source said anonymously.

The source also revealed that "the Houthis are currently holding several staff members of the United Nations Children's Fund (UNICEF) for questioning in the basement of the agency's headquarters in Sanaa."

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

The WFP is one of the largest humanitarian agencies operating in war-ravaged Yemen, where years of conflict have triggered what the United Nations describes as one of the world's worst humanitarian crises.