Protesters demanded the execution of factory bosses over the death of nearly 400 people in a building collapse Wednesday, as May Day became the focus of workers’ anger over Bangladesh’s worst industrial disaster.

Despite calls by the prime minister for “cool heads”, tensions over the country’s deadliest industrial disaster showed little sign of abating and there were fears of more violence and vandalism at textile mills.

Several thousand workers holding red banners and flags chanted “Hang the killers, Hang the Factory Owners!” as they took to the streets of Dhaka at the start of a series of nationwide demonstrations on what is a public holiday.

Kamrul Anam, one of the leaders of the Bangladesh Textile and Garments Workers League, said the workers were angry at “the murder” of their colleagues in the April 24 disaster at Savar on the outskirts of Dhaka.

“We want the severest punishment possible for those responsible for this tragedy,” he told AFP.Activists were expected to take to the streets across Asia, with tens of thousands expected to rally in Indonesia against outsourcing and low wages while major May Day protests are scheduled for crisis-hit Greece and Spain.

In impoverished Bangladesh, unions said demonstrations would be held in all the major cities.The first May Day protests were in the capital Dhaka, with police putting the number of demonstrators at around 10,000 although that figure was expected to mushroom later in the day.

The Bangladesh government faces foreign pressure to take credible moves to raise safety standards in the garment industry, with last week’s collapse at the Rana Plaza factory complex only the latest in a series of deadly disasters.

A total of seven people have so far been arrested and charged with “death by negligence” over the collapse of the eight-storey building which housed five separate garment factories.