A United Nations agency that defends human rights was ordered on Thursday to leave Venezuela by the government of President Nicolás Maduro, an extraordinary move that will further strip the country of foreign oversight at a time when its government has been accused of intensifying repression.

The announcement, by foreign minister Yvan Gil, comes just days after the detention and temporary disappearance of Rocío San Miguel, a prominent security expert and human rights advocate.

Following her detention, several United Nations entities issued online statements expressing concern about the arrest, some calling it part of a pattern in which the government tries to silence critics through intimidation.

Mr. Gil said he was giving the staff of the U.N. Office of the High Commissioner for Human Rights 72 hours to “abandon” the country.

Phil Gunson, a Caracas-based Venezuela expert for International Crisis Group, said the expulsion of the human rights agency, combined with Ms. San Miguel’s arrest, “marks a drastic hardening” by Mr. Maduro’s government of its actions against political opponents and critics.