Union leaders in southern Italy called for an immediate strike over the partial closing of the ILVA steel plant for environmental reasons.
The closure devastate the livelihood of union members, union leaders said.
"In five days, we will no longer have material to work with," a metalworkers union official said in Genoa.
A judge partially closed the plant, which makes 30 percent of Italy's steel, after an investigation of more than a decade into the facility's environmental impact.
Thousands of workers have taken to the streets to protest the judge's order, ANSA reported Friday.
The workers blockaded key roads in the area as police redirected traffic. A march to the Genoa prefecture was broken up when prefect Francesco Antonio Musolino convinced the marchers the court order could be repealed soon, ANSA said.
The plant employs 11,000 people, represented by three unions that called for an indefinite strike starting Friday.
The judge not only ordered a partial shutdown of the plant -- he also ordered the arrest of eight of the firm's top managers and former executives.