ADEN / SANAA, Yemen - Yemen's internationally recognized government on Saturday condemned the detention of 13 staff members from the United Nations (UN) and international and local non-governmental organizations (NGOs) in Sanaa, describing the move as an escalation of the country's ongoing humanitarian crisis.

The foreign ministry, in a statement, characterized the detentions as a "flagrant violation of international humanitarian law" and warned that they directly endangered the lives and safety of humanitarian workers.

The condemnation follows a Friday announcement by the UN, which declared it was suspending all official movements in Houthi-controlled northern Yemen due to the arrests. This suspension follows the detention of seven additional UN staff members by the Houthi group.

UN Secretary-General Antonio Guterres, in a statement, called the continued detention "unacceptable," and affirmed that the UN is actively working to secure the release of the detained individuals.

The Houthis have detained dozens of staff from the UN and other humanitarian organizations, mostly since mid-2023. In June 2024, the Houthis carried out a mass detention of staff from UN, international and local aid organizations in Sanaa, claiming they had detained "key members of an American-Israeli spy network" linked to the US Central Intelligence Agency.

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The UN has repeatedly called for the release of those detained, including during a December 2024 visit to Sanaa by World Health Organization Director-General Tedros Adhanom Ghebreyesus, who sought to negotiate their release.

Meanwhile, the Houthis on Saturday unilaterally released 153 war prisoners detained during the civil war with the Yemeni government forces in recent years, the International Committee of the Red Cross said.

Iscander Saeed, the spokesperson of the ICRC in Yemen, told reporters at a press conference in Sanaa that "Ansarullah (Houthis) today released 153 war prisoners unilaterally."

The ICRC welcomes this unilateral release, he added.

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"The ICRC has facilitated the initiative in the framework to encourage all sides to move ahead in this humanitarian file and release prisoners," he said.

Those released were handed over to their family members who had come to Sanaa from other provinces.

Yemen has been mired in a civil war since late 2014 when the Houthi group seized control of several northern provinces and forced the Saudi-backed Yemeni internationally recognized government out of the capital Sanaa.

The war has killed tens of thousands of people, displaced 4 million, and pushed the country to the brink of starvation, according to United Nations (UN) aid agencies.

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In May 2024, the Houthi group unilaterally released 113 war prisoners.

In April 2023, the UN facilitated the exchange of 900 prisoners between the Yemeni government and the Houthi rebel group. Thousands are still being held in prisons on both sides, including political opponents, human rights activists, and journalists.

The UN is trying to release of all detainees and reach a political settlement between the Yemeni sides to end the war.