UNITED NATIONS, Dec. 9 (Xinhua) -- UN Secretary-General Antonio Guterres condemns the Houthis' referral of UN staff to their special criminal court, his spokesperson said Tuesday.

"The Secretary-General is gravely concerned about the continued arbitrary detention of 59 United Nations personnel, in addition to dozens of NGO (non-governmental organization), civil society, and diplomatic mission personnel," spokesperson Stephane Dujarric said in a statement.

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

"United Nations personnel, including those who are nationals of Yemen, are immune from legal process in respect of all acts performed by them in their official capacity," it said.

The United Nations calls on the Houthis to rescind the referral and work in good faith toward the immediate release of all detained personnel of the United Nations, NGOs and diplomatic community, it said.

"The United Nations remains committed to supporting the people of Yemen and delivering principled humanitarian assistance," it added. ■