Hundreds of thousands of garment workers walked out of their factories in Bangladesh Thursday, police said, to protest the deaths of 200 people in a building collapse, in the latest tragedy to hit the sector.

Grief turned to anger as the workers, some carrying sticks, blockaded key highways in at least three industrial areas just outside the capital Dhaka, forcing factory owners to declare a day's holiday.

"There were hundreds of thousands of them," said Abdul Baten, police chief of Gazipur district, where hundreds of large garment factories are based. "They occupied roads for a while and then dispersed."

Police inspector Kamrul Islam said the workers had attacked several factories whose bosses had refused to give employees the day off.

"They were protesting the deaths of the workers in Savar," he said, referring to the town outside Dhaka where Wednesday's collapse of an eight-storey building housing five garment factories took place, injuring more than 1,000 people.

"Many wanted to donate blood to their fellow workers," he added.

Some 1,500 workers marched to the Dhaka headquarters of the main manufacturers association, demanding the owners of the collapsed factories be punished.

"The owners must be hanged," one protester cried, as others tried to lay seige to the headquarters.

Some workers smashed windows and vehicles before they were chased away by police, Wahidul Islam, a deputy commissioner of Dhaka police, told AFP.

Rescuers in Savar pulled dozens of bodies from the collapsed building on Thursday as the death toll in the country's worst industrial disaster reached 200, police said.

Managers had allegedly ignored workers' warnings that the building had become unstable.

Survivors say the building developed cracks on Tuesday evening, triggering an evacuation of the roughly 3,000 garment workers employed there, but that they had been ordered back to production lines.

The accident has again highlighted safety problems and poor working conditions that plague the textile industry in Bangladesh, the world's second-biggest clothing exporter.

Last November a blaze at a factory making clothing for Walmart and other Western labels in Dhaka left 111 people dead, with survivors describing how fire exits were kept locked by site managers.