The Free Union of Iranian Workers says several workers at the Isfahan Steel Company have been arrested in recent days amid rallies in the area of the industrial complex over their conditions.
Riot police broke up a rally during the strike by hundreds of workers at the country's third-largest steel producer. The workers have been on strike since February 25, demanding better conditions and higher salaries.
The union said workers had no information about the status of their arrested colleagues and due to the fact that the arrested workers were scattered across different departments, their exact numbers and names are not known.
Workers at the Isfahan Steel Company have gone on massive strikes several times in recent months.
Labor protests in Iran have been on the rise since last summer in response to declining living standards, wage arrears, and a lack of insurance support. Labor law in Iran does not recognize the right of workers to form independent unions.
Security forces across the country have been trying to suppress months of anti-government protests triggered by the September death of 22-year-old Mahsa Amini while in police custody for allegedly wearing a head scarf improperly.
The protests over Amini's death came after a summer of unrest across Iran over poor living conditions, water shortages, and economic difficulties resulting from crippling sanctions that the United States has imposed on Iran over its nuclear program.
The activist HRANA news agency said that more than 500 people have been killed during the unrest, including 70 minors, as security forces try to stifle widespread dissent.
Thousands have been arrested in the clampdown, with the judiciary handing down harsh sentences -- including the death penalty -- to protesters.