Iranian authorities arrested an aide to the defeated presidential candidate Mir-Hossein Mousavi, the satellite Press TV reported on Wednesday.
In the late hours of Tuesday night, Mir-Hamid Hassanzadeh was detained in the office of Iranian Student News Agency (ISNA), the report said.
According to Press TV, Hassanzadeh has been arrested in connection with his work at Mousavi's official website which he ran during the election campaign. He has already quit his cooperation with the website.
Working as an advisor to ISNA currently, Hassanzadeh was also a former manager of the news agency, Xinhua reported.
Iranian authorities have arrested dozens of reformists, political activists and more than 1,000 protesters in the unrest after the declaration of the presidential election results.
On June 13, the Iranian Interior Ministry said Mahmoud Ahmadinejad won 62.63 percent of the total ballots in the June 12 presidential election, while his main rival Mir-Hossein Mousavi got 33.75 percent.
Mousavi's supporters, claiming that the presidential election was rigged in favor of Ahmadinejad, participated in massive rallies in Tehran and other cities following the disputes.
The authorities said most of the detainees have been released.