Parastou Dokouhaki and Marzieh Rasouli, two widely read female bloggers were arrested most recently with little news coverage. Friends of the two started a Web site to draw attention to their situation.
Sahamoddin Bourghani, national press director for the Ministry of Culture under former president Mohammad Khatami, was also arrested Jan. 17, The New York Times reports.
Other arrests include freelance health and science reporter Fatemeh Kheradmand, ethnic researcher Ehsan Houshmandzadeh and Said Madani, a former university professor who edited a quarterly journal called Social Welfare.
Most, if not all, of the journalists arrested share a background in social activism, the Times said.
The Committee to Protect Journalists says at least 42 journalists were imprisoned in Iran last year.
Mohammed Abdel Dayem, the group's program coordinator for the Middle East and North Africa said: "Tehran is sending a message to the opposition media that dissent will be treated with a heavy hand. Not only are Iranian authorities detaining more journalists, but they also persist in mistreating those who have spent time in official custody."