The three were on their way to India to attend a journalism workshop on January 27 when they were arrested.
They were released the next day after being interrogated.
RSF says the arrests are an attempt by Iran's government to ban all contact with foreign journalists and organizations.
Another rights group, the Observatory for the Protection of Human Rights Defenders, has also expressed concern about the incident, and called on Iran to put an immediate end to the judicial proceedings against the three women.
The three have been involved in a campaign aimed at the elimination of all forms of legal discrimination against women.
Women in Tehran (epa file photo)
CALLING FOR MORE RIGHTS: Although women played key roles in Iran's 1979 Islamic Revolution, the place of women in post-revolutionary society has been a vexing question. Iranian women have struggled to bring attention to their calls for greater rights in their country's rigid theocratic system, calls that have often clashed with the values proclaimed by conservatives in society. (more)
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