Police in Bangladesh have opened fired at a protest by former workers of a factory making clothes for western retailers that collapsed, who had taken to the streets to complain at their treatment by the authorities since the disaster six weeks ago.

The protests took place close to the site of the former Rana Plaza factory, now entirely demolished, in Savar, Many garment factories are concentrated in the town near the capital Dhaka. The death toll from the Rana Plaza disaster now stands at 1,130.

Hundreds of protesters, including former workers as well as relatives of victims killed or injured, were demonstrating to demand compensation or outstanding salaries promised by the government and the main body representing local employers in the booming industry, the Bangladesh Garments Manufacturers and Exporters Association (BGMEA).

Sheikh Farid Uddin, a Savar police official, said: "Workers protested for their compensation and back pay. They stopped traffic on the highway for three hours. We requested them to clear the road but they became agitated and began damaging public transport [vehicles]. We have detained two people."

Protesters denied causing any damage.

"We did not commit any vandalism but still the police opened fire and [used] teargas," said Fatema Khatun, 20, a protester and survivor of the collapse, who said she had yet to receive outstanding pay.

According to the local newspaper Prothom Alo, around 50 people were injured when police charged with batons. Police officials said any firing had been directed into the air. There have been several such protests in recent weeks. The BGMEA says outstanding dues have been paid.

The clashes came as Alan Duncan, the UK minister for international development called for retailers who source garments in Bangladesh to assume responsibility for the clothes they sell "from the shop to the sewing machine".

On the first visit by a senior British official to Bangladesh since the Rana Plaza collapse, Duncan said such firms had a duty of care to those who made products sold on high streets.

The British retailers Primark and Matalan have admitted sourcing clothes in the Rana Plaza factory. Official investigations have blamed poor construction and corruption for the collapse. The owner, Sohel Rana, has been detained.

The garment industry in Bangladesh now exports $20bn (£13bn) of clothes each year. However, accidents are common. Last year, 114 people died in a fire.

Duncan told the Guardian: "The challenge is to cope with the success of this sector. In one sense, this is a fantastic development story. But there are large defects, and these exist because the setting of standards of employment rights, health and safety at work and building construction have not kept pace."

Last month's disaster was one of the world's worst industrial accidents. It has prompted criticism of major brands, which have been accused of sacrificing protection of workers in pursuit of profits.

Companies including Primark, Marks & Spencer, Mothercare and Next have recently signed up to a legally binding agreement committing them to improving and monitoring conditions in factories where clothes are sourced.