UN Secretary General Antonio Guterres has called for the immediate and unconditional release of 11 UN staff arrested by Houthi authorities in Yemen.

The workers were detained by security forces in raids on the World Food Programme (WFP), children's charity Unicef, and the World Health Organization (WHO), news agencies and the UN said.

Sunday's raids took place in the capital, Sanaa, and port city of Hudaydah, UN Special Envoy for Yemen Hans Grundberg said.

Grundberg mentioned that the Houthis had already been holding 23 other UN workers arrested since 2021.

Houthi authorities have not commented on Sunday's arrests.

In a statement, Guterres strongly condemned the arbitrary detentions, citing them as a severe hindrance to efforts delivering aid and advancing peace in Yemen.

The latest arrests occur amid heightened tensions following an Israeli attack that killed high-ranking Houthi officials, marking a significant escalation in the ongoing conflict since a civil war erupted in 2015.

The situation remains dire in Yemen, with significant casualties and millions of people in need of humanitarian assistance.