Fewer workers than usual have been gathering for cups of chai near the guarded, grey towers of Ashulia, a hub for garment factories on the outskirts of Dhaka. “Everyone seems scared of being harassed by the police,” says one tea seller, frowning from his stall.

Ashulia’s garment factories, which produce clothing for ranges on sale across the developed world, are alive with activity but the tension brimming in the air – and the lines of armed guards posted outside some gates – echo the anger that has swept the area.

Last month, tens of thousands of workers clocked in then immediately returned to the streets, joining the largest protests since those that followed the collapse in 2013 of the Rana Plaza clothing factory, causing more than 1,100 deaths.

The unrest over rates of pay forced around 50 factories to shut for more than a week and led to dozens of arrests and the “temporary dismissal” of at least 1,500 workers. Last week, those workers still willing to huddle in Ashulia’s streets during their lunch breaks were swapping stories about the people dismissed.

“No factories will give them work now,” one man in his late 20s says, asking that his name be withheld. “They are in big trouble. One of my friends told me he doesn’t even stay at his own house, afraid the police will harass him.”

Another worries that he will not be paid for the weeks in December when the factories were shuttered. “We get a very small amount of money,” he says. “If we do not get salary for two weeks, this will be a huge problem.”

“The officials of our factories get pay rises every year,” one of the men speaks up. “But they have all the problems when workers ask for a pay rise.”

The pay rise they wanted was a tripling of the minimum salary of 5,300 taka (£54) a month, currently the lowest minimum wage in the world, to 16,000 taka – still well short of what thinktanks such as the JustJobs Network, which has offices in Washington and New Delhi, consider a living wage.

Industrial unrest close to Christmas was particularly provocative, raising fears among factory owners that lucrative contracts with western brands such Gap, Zara and H&M could go unfilled. Police used rubber bullets to disperse the crowds of protestors and arrested at least 30 people, charging many under controversial wartime laws designed to quash threats to state security, union leaders claim.

Ashulia’s factories finally roared back to life on Boxing Day, but workers returned to find lists of names posted at the gates. “Around 59 garment factories had temporarily dismissed their workers and asked them for explanations why their contracts should not be terminated,” says Babul Akhter, head of the Bangladesh Garments and Industrial Workers’ Federation.

Bangladeshi garment workers have not had a pay rise since 2010. Photograph: Sk Hasan Ali/Corbis via Getty Images

Police said about 1,500 workers had been sacked or suspended but Akhter says the actual number “may be as much as 3,000”. Among those to see their names posted that morning was Rajan Chandra Gain, 19, a cutting assistant at Ashulia’s Fashion Forum Ltd factory. He insists he played no part in the demonstrations.

“We had heard of the protests going on outside,” he says. “But I was working at my station. Soon everyone was asked to leave. I followed. The factory was shut down for the day. [When I returned] I found my photo on the notice saying I have been temporarily dismissed along with a few others.”

The days since have been anxious ones for Gain. “I am one of six siblings from my 13-member family who are working,” he says. “The entire family depends on our incomes. If I do not get my job back, my family will be in a tough financial situation.”

But it isn’t just losing money that the teenager fears. Rumours abound that a blacklist of troublemakers is doing the rounds of factories in the area. “I have heard from other workers that the list has also been provided to the law enforcement authorities,” Gain says. “I am scared that I may be arrested. Even if I am not, [if] I do not get my job back at this factory, I may not find another job in any other ready-made garment factory because of what has happened here.”

Another worker who discovered his name on the notices is Humayun Kabir, 30, a sewing machine operator who had worked at the Setara Group factory for nearly six years – until he was provisionally fired. “I still do not know what my crime was and why I was dismissed,” he says.

His wife works at a garment factory nearby, and together the couple support four children and Kabir’s mother on 14,000 taka a month. This month they’ll need to get by on half that much. “We have not been able to pay our house rent of 3,500 taka,” he says.

It could be worse: Kabir is still free, unlike another garment worker, Jahangir, who was arrested during the protests and is being held in Dhaka prison. His wife, Jharna Begum, spoke to the Observer by phone from the jail, where she was visiting him. “We are going through a very tough time,” she said. “I am particularly concerned about my two children. I don’t know what’s in store for us.”

The last time minimum wages were increased was 2013, the same year the eight-storey Rana Plaza factory in the Savar area collapsed, killing 1,134 people. The disaster brought Bangladesh’s entire garment industry under intense scrutiny but did not slow its strong growth, from $21.5bn that year to $28bn in 2015-16.

Wages also rose in 2006 and 2010, each time preceded by significant protests. Hasnain Malik, head of equity research at London-based investment bank Exotix Partners, suggests December’s unrest could be the first shots in new wage negotiations.

In the past, too, unions have initially demanded a tripling in wages, eventually settling for an 80% hike. Even with an increase of he same amount this time, Malik notes, “you’d still be seeing Bangladesh as a location on the lower end of global wages in this industry”.

But others see the protests as signs of deeper trouble. “This issue is much bigger than wages,” says Sabina Dewan, the president of the JustJobs Network.

In virtually a single generation, the apparel sector has lifted millions of Bangladeshis out of subsistence lifestyles, but failed to take them any higher, she says. “Many countries have started with a low value-added apparel manufacturing, and then moved up the value chain. But you have to use apparel as a springboard. The growth it generates needs to be distributed as better wages, safety nets, and more benefits for the people,” she says.

“Otherwise workers are being used as a mode of production, but none of the benefits are accruing to them … and at the end of the day, people are going to speak up, people are going to revolt,” she adds.

At Ashulia, people are back at their workstations, if only for now. Bangladesh’s largest lobby of factory owners insists it will not enter into new wage negotiations until 2018.

They have the backing of the country’s labour minister, Mujibul Haque. “There is no scope to increase the wages of ready-made garment workers at this moment,” he says.