The Sunday report by the semi-official ISNA says Bagher Asadi was released based on bail. It remained unclear why authorities detained the 71-year-old Asadi. He is known as a pro-reform figure.
In mid-March, authorities detained Asadi, who previously held a senior position at Iran's U.N. mission. Asadi is an ally of former pro-reform President Mohammad Khatami.
In May, Foreign Minister Ali Akbar Salehi confirmed the arrest of Asadi, describing the incident as a possible "misunderstanding."