The Iran-backed Houthis on Sunday raided offices of the United Nations' food and children's agencies in Yemen's capital, detaining at least one UN employee, officials said, as the rebels tighten security across Sanaa following the Israeli killing of their prime minister and several Cabinet members.

Abeer Etefa, a spokesperson for the World Food Program, told The Associated Press that security forces raided the agencies' offices in the Houthi-controlled capital Sunday morning.

Also raided were UNICEF offices, according to a UN official and a Houthi official, who spoke on condition of anonymity because they weren't authorised to brief the media.