The United Nations has called for the immediate release of 11 of its personnel who have been detained by the Houthi rebels in Yemen.
UN spokesman Stéphane Dujarric said the world body was pursuing all available channels to secure their safe and unconditional release as rapidly as possible.
Several employees of other international organizations were also detained, according to reports quoting officials from Yemen's internationally recognized government.
Phones and computers were seized during the raids on the workers' homes and offices, which come after months of Houthi attacks on commercial ships in the Red Sea.
The Mayyun Organization for Human Rights said Houthi rebels officers targeted 18 aid workers from several groups in Amran, Hudaydah, Saada and Sana'a at the same time.
Officials said that multiple members of the US-backed National Democratic Institute (NDI) were targeted as well.