At least four union activists were arrested on the eve of another round of nationwide protests scheduled to be held on Labor Day, May 1, by Iranian teachers.

The Coordination Council of Iranian Teachers’ Trade Associations said that security officers raided the homes of the several activists in Tehran on Saturday, arrested four and confiscated their electronic devices.

The spokesman of the association, Eskandar Lotfi, said in a tweet that three of the detainees were taken to the notorious Evin prison, adding that tens of their other colleagues from different parts of the country have been summoned to court.

According to reports, the officers used violence against some of the activists who resisted arrest, including Rasoul Badaghi, and broke glasses and furniture with a hammer.

During the latest round of nationwide rallies, demonstrators gathered in front of the Education Ministry building in Tehran on Thursday and its offices in various other cities to protest discriminatory regulations on a teacher ranking plan as well as the "continuous and systematic" suppression of union activists.

Teachers across Iran have staged several nationwide protests and strikes in the past six months and have vowed to continue protests until authorities meet their demands including, the implementation of decade-old legislation that would bring the salaries and pensions of 750,000 teachers in line with other civil servants.