Police fired rubber bullets and tear gas at thousands of Bangladesh garment workers on Sunday during a second day of protests to demand a $100 minimum monthly wage, police said.

Protesters threw stones and bricks at factories just outside the capital in Kaliakoir that make clothes for some of the world's top retailers. Others marched along a key highway and blocked traffic, police said.

"We were forced to fire rubber bullets and tear gas to disperse the workers who attacked about half a dozen factories," Kaliakoir police chief Omar Faruq told AFP, adding that some 6,000 workers took part in the protests.

Bangladesh is the world's second-largest garment exporter with apparel shipments from its 4,500 garment factories accounting for 80 percent of its $27 billion annual exports.

But the vast majority of the impoverished nation's three million workers earn a basic monthly wage of 3,000 taka ($38) -- among the lowest in the world -- following a deal between unions, the government and manufacturers in August 2010.

On Saturday, dozens of factories were forced to shut after at least 20,000 workers left their machines to demand the wage rise.

Angry demonstrators hurled stones at the outside of some 20 factories after managers refused to allow some employees to join the protests, police said.

Faruq said protesters on Sunday left the highway after about an hour.

In June this year, the government set up a panel to review salaries and unions have demanded an 8,114 taka ($100) minimum monthly wage.

Factory owners have rejected the demand, saying they can raise wages by only 20 percent to 3,600 taka due to gloomy global economic conditions.

Protests over poor wages, benefits and working conditions have shaken Bangladesh's garment sector, the country's economic mainstay, since April when a factory complex collapsed, killing over 1,100 people.

The collapse, one of the world's worst industrial disasters, highlighted appalling working conditions in the garment factories, where employees toil for 10-12 hours a day for low wages.

Widespread protests seeking wage rises in 2006 and 2010 led to deadly clashes, leaving dozens of workers dead and hundreds of factories vandalised.