Miners at Chile's Collahuasi mine walked off the job Saturday, complaining repeated demands over pay and working conditions have not been met.

The Collahuasi mine produces about 3 percent of the world's copper and the strike there follows a week-old strike at the larger Escondida mine.

The Escondida mine accounts for 7 percent of the world's copper output.

Chile is the world's largest producer of copper. The strikes come as copper prices have been rising, boosting profits for mine owners.

Some officials have voiced concerns that the Collahuasi and Escondida strikes could inspire other miners to put down their tools and demand larger concessions from the companies that own the mines.