Iranian-US student Esha Momeni, who had been released on bail after being held on security charges, has been banned from leaving the Islamic republic for one month, judiciary spokesman Ali Reza Jamshidi said on Tuesday.
"Ms Momeni was banned from leaving Iran a week ago," Jamshidi told reporters.
"Her passport had been given to her but a new issue has opened and the examination of this issue will take about one month," he said, without giving further details.
The student, who holds both Iranian and US nationality, was detained in Tehran on October 15 and released on bail on November 11.
Judiciary officials said that her detention was based on the charge of action against national security. But in late October, Momeni's lawyer Mohammad Ali Dadkhah told AFP the student was arrested for involvement with a women's rights equality campaign.
Momeni, a graduate student at the Northridge campus of California State University, had travelled to Iran to do research for her thesis on women's rights.
Iran does not recognise dual nationality and has in the past said the arrest of US-Iranian citizens is an internal matter.
Over the past year, Iran has arrested several women who backed a One-Million-Signature campaign, launched two years ago to call for changes to Iranian laws deemed discriminatory to women.
The judiciary spokesman also said that Iran had put on trial four people for plotting to overthrow the government, backed by the US Central Intelligence Agency (CIA).
"A network attempting to bring about a soft overthrow (of the government) has been found. Four people have been arrested and were tried," Jamshidi said.
"They were linked to the CIA, backed by the US government and State Department... They recruited, trained and dispatched people to different countries."
More details would be made public "within two days," Jamshidi added.
The Iranian judiciary has recently disclosed details on a series of cases involving charges against opposition groups, including those said to have links abroad.
Tehran accuses Washington and London of backing violent and non-violent anti-regime actions.