Ezatollah Sahabi, a former member of parliament and prominent opposition figure, was buried on June 1 after he died of a stroke in Tehran on May 31.
Sahabi's daughter, Haleh, an opposition activist and women's rights campaigner, died shortly after the funeral following what opposition supporters described as a scuffle with security forces at the ceremony.
Activist Morteza Kazemian told Radio Farda that Habibollah Peyman, a member of the Freedom Movement of Iran, political activist Hamid Ahrari, and Hamed Montazeri, the grandson of the late dissident cleric Grand Ayatollah Hossein Ali Montazeri, were among those detained at the funeral.
The official Islamic Republic News Agency (IRNA) also reported that five mourners were detained, without giving their names.
Haleh Sahabi, who was serving a two-year jail sentence on charges of “spreading propaganda against the regime" and "disrupting public order," had been granted leave from prison to attend her father's funeral.