About 700 garment factories in Bangladesh were shut Tuesday after days of violent protests by tens of thousands of workers demanding better wages.

The manufacturers decided late Monday to close their factories because they had no other way to avoid the anarchy in the major industrial hub outside the capital, according to an official at the Bangladesh Garment Manufacturers and Exporters Association. The news is likely to undermine confidence in the country's ability to replace China as a low-cost source for apparel and footwear production

But the shut doors spurred more violence Tuesday, when workers smashed vehicles and set fire to at least five on a major highway, local police chief Sirajul Islam told the Associated Press. He said at least 30 people were injured after security officials used batons and tear gas to break up the demonstration.

“We are helpless,” Shafiul Islam Mohiuddin, a vice-president of the industry group, told The Associated Press by phone.

“We have decided to keep the factories closed for an indefinite period,” he said.

He said the garment factories were missing buyers' deadlines because of the continuous unrest.

Over the last few days, thousands of workers took to the streets and attacked many factories in Ashulia. Hundreds have been injured in clashes with police, who are trying to remove them from streets and stop the violence.

The workers are demanding that the minimum wage rise to 5,000 takas ($73) a month. The current average monthly salary is 2,000 takas ($29).  That makes them the world's most poorly paid garment workers, according to the International Trade Union Confederation, a Vienna-based labor rights group.

Bangladesh has some 4,000 garment factories that export mainly to the United States and Europe. Garment exports earn the country $12 billion. The industry employs 2 million people in Bangladesh and is a mainstay of the impoverished country's economy.