Tehran, Iran (CNN) -- Iranian authorities have arrested several journalists, including the editor-in-chief of a leading reformist newspaper, on accusations of collaborating with the regime's opponents and working for foreign news organizations.
Acting on a court-issued warrant, security officers detained several journalists at their work places Sunday, the semi-official Mehr News Agency reported. The publications raided by officials included the newspapers Etemaad, Bahar, Arman and Shargh, it said.
The news agency reported that it appeared that some of those detained had been working with Farsi-language counterrevolutionary media outlets.
In Iran's tightly managed news industry, the term counterrevolutionary implies overseas involvement. Several prominent Western news groups run services in Farsi, the primary language in Iran, including the BBC and Voice of America.
Iran has taken a hard line on journalists and bloggers in recent years, following the crackdown on the massive protests that took place over the disputed 2009 election.
In a report published last month, the New York-based Committee to Protect Journalists said Iran had the second highest number of journalists behind bars (45) in the world last year after Turkey (49).
Mashregh News, a pro-government news website affiliated with conservative lawmakers in Iran, reported the names of five journalists among those taken into custody.
It described the detainees as being "close to the plotters," a term the Iranian regime uses for its opponents.
Those arrested in Iran over the weekend included Javad Daliri, the editor-in-chief of Etemaad, a reformist daily newspaper, according to Mashregh News. Daliri has previously served prison sentences after being convicted of working with opponents of the regime.
Two other Etemaad staff members, Sasan Aghaie and Nasrin Takhiri, were also detained.
Soleyman Mohammadi, an editor at the daily newspaper Bahar, was arrested. Mohammadi recently gave an interview to a French radio station in which he suggested that Iran's official rape statistics were falsified.
Another journalist detained, Milad Fadaie, the political editor for Iran Labor News Agency, had been arrested twice before by authorities.
Mehr reported Sunday that more information on the arrests would be disclosed soon.
CNN's Sara Mazloumsaki in Atlanta contributed to this report.