Iranian security forces opened fire at people who gathered at a cemetery in Mahsa Amini’s home town of Saqez on Wednesday to mark 40 days since she died in police custody, a witness said.

“The riot police shot mourners who gathered at the cemetery for Mahsa’s memorial ceremony … dozens have been arrested,” the witness said.

Demonstrations ignited by the 22-year-old’s death on September 16 have become one of the boldest challenges to the Islamic Republic’s clerical leadership since the 1979 revolution.