Dozens of the supporters of the main Iranian opposition organization, People’s Mojahedin of Iran (PMOI or MEK) paid tribute to political prisoners who were mass executed and buried in 1988 in a mass grave in the city of Mashhad, north-east Iran.
Transcript of the remarks by a PMOI activist who filmed the tribute at the mass grave in Behesht-e-Reza cemetery are provided here:

In the name of God
It is August 1, 2016. Here is Behesht-e-Reza in city of Mashhad (northeast Iran), adjacent to section 22.
Here is where the PMOI (MEK) martyrs from years 1981 to 1988 were buried.
We have come here to commemorate the memory of 30,000 red roses who were martyred by the anti-human clerical regime.  Following drinking the “chalice of poison” and accepting the cease fire in the Iran-Iraq, this regime resorted to massacre of PMOI political prisoners and other activists who did not succumb to Khomeini. The martyrs were buried in mass graves.
About 70 of these martyrs are buried in these two rows.
On the 28th anniversary of the massacre of martyrs, we vow to bring to justice all the masterminds and perpetrators of this genocide against the PMOI, so justice would prevail, humanity would find out what we went through and the repetition of this crime be prevented.
At the end, we repeat that we neither forget, nor forgive this crime.