A deadly fire has swept through a clothes factory on the outskirts of Bangladesh's capital, Dhaka, killing at least 100 people, Al Jazeera's Nicolas Haque reported.

The fire at the nine-story factory, operated by Tajnin Fashion, in the Ashulia industrial area, started on the ground floor on Saturday night and quickly spread. Firefighters took nearly five hours to extinguish the flames.

Many of the employees fled the flames on the first floor and went to the top of the building, becoming trapped.

Most of the victims died because they jumped from the building to escape the flames, a police official said. The death toll could still rise, witnesses said.

The cause of the fire, according to the authorities, was a bad electrical circuit.

"There's an investigation underway to try to find out [exactly] what caused this accident," Haque said, adding that similar accidents "happen often".

Since 2006, more than 600 people have died in Bangladesh because of fires and lack of safety standards in crowded factories.

Bangladesh has around 4,500 garment factories that make clothes for brands including Tesco, Wal-Mart, JC Penny, H&M, Marks & Spencer, Kohl's and Carrefour.

Ready-made garments account for 80 per cent of the country's $24bn annual exports.

Haque said that labour groups he spoke to claimed that factories "are simply not equipped to the safety standards that are required to meet the demands of Western brands".

"If you speak to garment managers, they say that they are under pressure to produce as much clothes as possible with the least amount of money," he said. "And so they say in these circumstances, safety isn't always the priority."

"The priority here is to produce as much clothes as possible."

Activists said they hope that the latest incident could force the government to reset the garment industry's safety standards.

Flyover accident

Meanwhile, in the southeastern port city of Chittagong, a flyover under construction collapsed, killing at least 13 people.

Dozens are feared missing.

"So far, 13 dead bodies have been recovered," sub-inspector Mohammad Alauddin told AFP.

Another police officer, Shakakhawat Hossain, said dozens could be trapped under the debris.

Hossain said about 20 people were injured, including some during clashes between police and an angry crowd that attacked the site offices of the construction company after the flyover collapse on Saturday evening.