UNITED NATIONS - UN Secretary-General Antonio Guterres strongly condemns the continued arbitrary detentions of UN personnel and its partners, as well as the ongoing unlawful seizure of UN premises and assets in areas under Houthi control, a UN spokesperson said on Monday.

The condemnation came after the Houthi de facto authorities in Yemen detained nine additional UN personnel recently.

With the latest detentions, the total number of arbitrarily detained UN staff in Yemen since 2021 has risen to 53, Stephane Dujarric, spokesperson for the UN chief, said in a statement.

Noting that these actions hinder the United Nations' ability to operate in Yemen and to deliver critical assistance, the statement said the secretary-general remains deeply concerned about the safety and security of UN personnel in Yemen.

Guterres reiterated his urgent call for the immediate and unconditional release of all personnel from the United Nations, non-governmental organizations, civil society organizations and diplomatic missions, the statement said. "They must be respected and protected in accordance with applicable international law."

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The UN chief also reiterated that UN personnel must be allowed to independently perform their functions without hindrance, the statement said, adding that the premises and assets of the United Nations are inviolable and must be protected at all times, consistent with the UN Charter and the Convention on the Privileges and Immunities of the United Nations.

"The United Nations will continue to work tirelessly, and through all available channels, to secure the safe and immediate release of all arbitrarily detained personnel, as well as the return of UN agency offices and other assets," the statement noted.

"The secretary-general remains steadfast in the UN commitment to support the people of Yemen and their aspirations for a just and lasting peace," it said.