Iran's intelligence ministry said on Saturday that it had arrested a Swedish citizen on espionage charges.
"The intelligence ministry announced that a citizen of the Kingdom of Sweden was arrested on espionage charges," the official IRNA news agency reported, without naming the detained person.
The ministry did not say when the arrest was made.
Sweden's Foreign Ministry said it was aware of the case.
"This is a known and ongoing case, which the Foreign Ministry has been working on for a while," a spokeswoman said in an emailed comment.
She said the case is that of a Swedish man, whom the Foreign Ministry had announced in May as being detained in Iran. Iran did not report that arrest at that time.
Iran's semi-official Fars news agency quoted the intelligence ministry as saying the suspect had been under surveillance during several previous trips to Iran "because of [their] suspicious behaviour and contacts … for visiting cities that were entirely outside of tourist destinations”.
It said that the suspect had a history of travelling to the Israeli-occupied Palestinian territories "before leaving for Iran.”
In May, Sweden said a man had been detained in Iran, only days after it advised against unnecessary travel to the country, citing a deteriorating security situation.
Relations between Sweden and Iran are tense after the European country detained and put on trial a former Iranian official on charges of war crimes for the mass execution and torture of political prisoners at an Iranian prison in the 1980s.
On July 14, a Swedish court sentenced the man, Hamid Noury, to life in prison.
Iran condemned the verdict, saying it was “politically motivated” and had “no legal validity”.
The Iranian foreign ministry summoned the Swedish charge d'affaires in Tehran to protest the sentence.
Iran’s security forces have arrested dozens of foreigners and dual citizens in recent years, mostly on espionage and security-related charges.
Rights groups have accused the Islamic Republic of trying to win concessions from other countries through arrests on trumped-up charges. Tehran denies the accusations.