At least nine Yemeni employees of United Nations agencies have been detained by Yemen's Houthi rebels under unclear circumstances, authorities said Friday, as the rebels face increasing financial pressure and airstrikes from a U.S.-led coalition. Others working for aid groups also likely have been taken.

The detentions come as the Houthis, who seized Yemen's capital nearly a decade ago and have been fighting a Saudi-led coalition since shortly after, have been targeting shipping throughout the Red Sea corridor over the Israel-Hamas war in the Gaza Strip.