Iran says it has arrested a US-Iranian dual national facing spying charges who attempted to leave the country.
Judiciary spokesman Gholamhossein Esmaili did not identify the man, but said he "had been free on bail".
Iranian media reported last week that a US-Iranian businessman named Emad Shargi had been arrested has he tried to cross a western border illegally.
It could complicate plans by new US President Joe Biden to re-engage diplomatically with Iran.
His predecessor Donald Trump subjected the Tehran government to a "maximum pressure" campaign of crippling economic sanctions.
Mr Trump wanted to compel Iranian leaders to renegotiate a 2015 nuclear deal that he abandoned, but they refused to do so and retaliated by violating a series of key commitments.
Mr Biden has said he is open to rejoining the accord and easing the sanctions if Iran returns to full compliance.
Iran has detained a number of US-Iranian dual citizens and Iranians with US permanent residency in recent years, most of them on spying charges.
At a news conference on Tuesday, Mr Esmaili responded to a question about the reported arrest of an US-Iranian "defendant".
He said Iranian law did not recognise dual nationality, but that "the defendant had been free on bail... and was arrested as he tried to leave the country". This person "faced charges from earlier in the area of spying and gathering information for foreign countries", he added.
Earlier this month, Iran's Young Journalists' Club (YJC) news agency reported that Emad Shargi, who it said worked at an Iranian venture capital company called Sarava Holding, had been arrested on after "trying to illegally flee the country from western borders".
Iran has detained another U.S. citizen, Iranian-born businessman Emad Sharqi, while he was trying to leave the country. https://t.co/nIYwVprF3j— IranHumanRights.org (@ICHRI) January 19, 2021
The YJC said he had been previously sentenced to 10 years in prison for "espionage and military intelligence gathering", but had been released on bail ahead of an appeal.
A family friend of Mr Shargi told the US network NBC that he had been summoned to a court in Tehran on 30 November and told that he had been convicted of espionage without a trial.
A year earlier another court had cleared him of the charge, but authorities had not returned his Iranian and US passports, the friend said.
Mr Shargi's family said he was being held incommunicado.
"We just pray for his health and safety," NBC quoted a statement as saying. "It's been more than six weeks since he was taken and we have no idea where he is or who has him."
In a separate development last week, US authorities arrested an Iranian academic near his home in Boston on charges of "acting and conspiring to act as an unregistered agent" of the Iranian government.
Prosecutors said Kaveh Lotfolah Afrasiabi was "a secret employee of the government of Iran and the permanent mission of the Islamic Republic of Iran to the United Nations (IMUN) who was being paid to spread their propaganda".
A spokesman for Iran's foreign ministry denied the allegation and condemned the arrest as "a clear hostage-taking of Iranian nationals".