A protest in Dhaka in April on the third anniversary of the Rana Plaza garment factory disaster that killed over 1,100 people (AFP Photo/Munir Uz Zaman)

Dhaka (AFP) - Dozens of garment factories in Bangladesh shut down Thursday as a workers' strike escalated over a pay claim.

The Bangladesh Garment Manufacturers and Exporters Association (BGMEA) closed 55 factories in a suburb on the outskirts of Dhaka, association president Siddikur Rahman said, after police arrested at least seven people who were leading the strike.

"Those (factories) will remain closed until the government says it is safe to reopen them," Rahman told AFP.

Workers went on strike nine days ago to protest the firing of 121 colleagues and soon added a pay hike to their list of demands.

The protest escalated earlier this week when police fired rubber pellets, injuring 10 demonstrators according to labour leader Taslima Akhter.

Several hundred policemen have since been deployed in the industrial zone, home to the factories which supply leading Western retailers such as GAP, Zara and H&M.

The workers want their salaries to be tripled from 5,300 taka ($67) -- the current monthly minimum wage -- to 16,000 taka.

The government raised the minimum wage for garment workers to 5,300 taka in 2013 after the industry came under intense international scrutiny over a series of disasters that killed scores.

But even after the increase, Bangladeshi garment workers remain among the lowest paid in the textile sector in the world.

Industry official Rahman said there was "barely a chance" of a further salary hike, citing a law that only allows salaries to be reviewed once every five years.

Bangladesh's $30 billion garment industry has a woeful history of poor pay and conditions for its four million workers.

The garment workers have vowed to continue the strike until their demands are met.

Garment manufacturing makes up 80 percent of Bangladesh's exports and a prolonged interruption would have a cascading impact on the impoverished country's economy.

Protests over poor wages, benefits and working conditions are frequent in Bangladesh, but gained intensity after the collapse of the Rana Plaza factory complex in April 2013, which killed 1,138 people.

The tragedy triggered international outrage, forcing US and European clothing brands to improve deplorable safety conditions at the factories that supply them.