The UN has called for the immediate release of 11 of its personnel who have been detained by the Houthi movement in Yemen.

The employees were taken in various parts of the conflict-torn country, in what appears to be a co-ordinated crackdown.

UN spokesman Stéphane Dujarric said the world body was pursuing all available channels to secure their safe and unconditional release as rapidly as possible.

The armed group sees itself as part of an Iranian-led “axis of resistance” against Israel, the US and the wider West, and has declared its support for Palestinians in the Gaza Strip.

The Houthis have been targeting commercial shipping in the Red Sea, triggering retaliatory air strikes by the US and its allies.

Several employees of other international organisations were also detained, reports quoting officials from Yemen’s internationally recognised government said.

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 Organisation for Human Rights said Houthi intelligence officers targeted 18 aid workers from several groups in Amran, Hudaydah, Saada and Sana’a at the same time.

Officials told Reuters news agency that multiple members of the US-backed National Democratic Institute (NDI) were targeted.

The detentions demonstrate the risks facing aid workers in a country where a decade-long civil war has reportedly killed more than 150,000 people and triggered one of the world’s worst humanitarian crises.

They come as the Houthis face increasing economic difficulties and air strikes carried out by a US-led coalition.

The armed group controls the capital of Yemen – Sana’a – and the country’s north-west, running a de facto government which collects taxes and prints money.

The internationally recognised government of Yemen is based in the southern port of Aden.