​​​​​​​ISTANBUL

UN Secretary-General Antonio Guterres expressed "grave concern" Tuesday about the "continued arbitrary detention" of 59 UN personnel in Yemen, in addition to civil society and diplomatic mission staff.

Guterres also condemned the Houthis' referral of UN personnel to their special criminal court, spokesperson Stephane Dujarric told reporters.

"The UN personnel have been held incommunicado, some for years, without any due process, in violation of international law," said Dujarric.

He emphasized that UN personnel, including Yemeni nationals, are immune from legal process for acts performed in their official capacities.

"We don’t want to be in this court and we want them to be released," he added.

The UN demanded that the Houthis rescind the referral to the court and "work in good faith toward the immediate release of all detained personnel."

Dujarric said the UN remains committed to supporting Yemenis and delivering "principled humanitarian assistance."

Yemen fell into a civil war since the Iran-backed Houthi group seized control of the nation’s capital of Sanaa in 2014, forcing the legitimate government to flee to the south.