Iran’s Free Labor Union (FLU) reported on Thursday that security forces attacked a protest gathering of teachers, held outside the ministry of education offices in Isfahan.

Active and retired teachers were holding a protest for low salaries and demanding the release of teacher activists from prison.

A video circulated by FLU on its Telegram channel shows the aftermath of tear gas used by security forces against the protesters. The report also says police arrested two or three protesters, but officials have not commented on the news.

Retired teachers also demand their pensions to be adjusted after Iran’s currency gradually lost value in 2018. Teachers groups have frequently held protests in Iran in the past two years, because of low salaries and substandard schools.

Currently, several teachers’ rights activists are in prison, charged with “security” offenses.

Iranian rights activists and groups, as well as international human rights organizations have demanded the release of detained teachers.