Thousands of workers in Bangladesh have protested to demand a $100-a-month minimum wage, forcing hundreds of garment factories to shut down for the day.

Workers took to the streets for a third day on Monday, blocking major roads and attacking vehicles in the Gazipur and Savar industrial zones, on the outskirts of the capital, Dhaka.

Abdul Baten, police chief of the Gazipur industrial district, which is home to hundreds of factories, told the AFP news agency that "up to 200,000 workers" had joined the latest demonstrations.

$100 is the minimum we have asked for. A worker needs much more than that to lead a decent life Shahidul Islam Sabuj, Union Leader

At least 50 people, including some policemen, were injured, witnesses and police said, as police fired tear gas and rubber bullets, and workers responded by throwing broken bricks.

Baten's deputy Mustafizur Rahman also said about 300 factories, which make clothing for Western retailers such as Walmart, were shut on Monday to contain the violence, as protesting workers attacked plants that stayed open.

The monthly minimum wage in Bangladesh is $38. The government is in talks with unions and factory owners on a new minimum wage.

Bangladesh last increased its minimum garment-worker pay in late 2010 in response to months of street protests, almost doubling the lowest pay. Recently, factory owners offered a 20 percent pay rise which workers refused, calling it "inhuman and humiliating".

Union leader Shahidul Islam Sabuj threatened to continue the protests, which were also staged on Saturday and Sunday, until wages are increased.

"One hundred dollars is the minimum we have asked for. A worker needs much more than that to lead a decent life," he told AFP.

Deadly incidents

Garments are a vital sector for Bangladesh and its low wages and duty-free access to Western markets have helped make it the world's second-largest apparel exporter after China.

But the $20bn a year industry, which supplies many Western brands, has been under the spotlight after a series of deadly incidents, including the collapse of a housing factory in April that killed more than 1,130 people.

The recent string of accidents has put the government, industrialists and the global brands that use the factories under pressure to reform an industry that employs four million and generates 80 percent of Bangladesh's export earnings.

This month, a group of retailers and clothing brands failed to establish compensation funds for the victims of Bangladesh factory disasters, as many companies that sourced clothes from the buildings decided not to take part in the process.