RSF ranked Iran at 166 out of 169 countries in its 2007 annual Press Freedom Index. Iran ranked 162 in the groups 2006 report.
The media rights watchdog said, As in the past, it is Iran that jails the largest number of journalists in the Middle East.
In Iran (166th), journalists are the target of very aggressive behaviour by the authorities, who tolerate no criticism or expression of political or social demands, it said, adding that eight journalists were currently languishing in Iranian prisons.
Many other journalists are facing serious, trumped-up charges that could result in their being imprisoned for criticising stoning or corruption, or for working for foreign news media, the report said.
The international press freedoms group frequently criticises media censorship and violation of journalists rights in Iran.