The letter, addressed to Tehran General-Prosecutor Abbas Jafari Dolatabadi, was published on July 28.
Tajik's family also recently wrote a letter to Iran's judiciary. That letter described a conversation between Tajik and his sister, Parvin, during a prison visit when he reportedly told her he had been "dishonored" on the first night of his arrest last month in the presence of a deputy prosecutor.
Tajik's lawyer, Mohammad Sharif, told Radio Farda that in Iranian judicial parlance, "being dishonored" is usually interpreted as "being sexually or physically assaulted."
In their letter, the journalists write, "It was not just Abdolreza Tajik who was dishonored. It is justice, law, and human rights that are being dishonored [because of his arrest and treatment]."
Tajik, a journalist and human rights activist, was arrested on June 12 for the third time since the disputed June 2009 presidential election. The charges against him are not known.