The statement claims an increasing number of students and political activists are facing "false" accusations of disrupting public order, insulting sacred values, or involvement in what officials have called a "creeping coup."
Farideh Gheyrat, a lawyer who signed the open letter, told Radio Farda that the recent arrests of workers, teachers, and students is very troubling for all human rights activists.
"The recent massive wave of arrests is unacceptable for rights advocates and those who care about human rights," Gheyrat said.
Gheyrat added that the letter's signatories are calling on Iran's leaders to prevent further arrests and to release those who have been detained in recent months.
The letter highlights the case of several detained students from Tehran's Amir Kabir University who, according to their families, have been tortured in prison.