Tens of thousands of Bangladeshis joined May Day protests Wednesday to demand the execution of textile bosses over the collapse of a factory complex, as rescuers warned the final toll could be more than 500.

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.

Bangladesh on Tuesday defended its decision to snub foreign aid after the collapse of a factory complex as anger flared at the recovery operation and towards the building's owner when he appeared in court.

With the death toll from the country's worst ever industrial disaster now standing at 382, Western retailers offered compensation to the victims of last Wednesday's tragedy on the outskirts of the capital Dhaka.

A blaze broke out in the wreckage of a Bangladesh factory block Sunday, killing a woman whose 110-hour battle for survival had touched the nation following its worst industrial disaster, the country's fire chief said.

Earlier, the owner of the complex, property tycoon Sohel Rana, was detained as he attempted to cross into India and was flown back to Dhaka where he will face charges over the building's collapse which has so far claimed 381 lives.

Rescue teams at the site of a collapsed factory block in Bangladesh where 363 people have died called in heavy-lifting equipment on Sunday as hopes of finding more survivors faded.

Four people were hauled out alive overnight more than 90 hours after the disaster, but the last feeble cries for help, still audible from inside the mountain of rubble early in the day, appeared to have ended.

Exhausted rescuers raced Saturday to dig out dozens of people found alive in the rubble of a Bangladesh garment factory complex that caved in three days earlier as the death toll rose to 324.

Police said they arrested two factory owners early Saturday as rescue workers pulled two survivors from the wreckage, giving fresh hope to the teams of firefighters, police and volunteers who worked through the night.

Rescue teams found around 50 people alive Friday on the third floor of a collapsed garment factory compound on the outskirts of the Bangladeshi capital, a fire brigade official said.

"We have found around 50 people still alive at several places on the third floor after digging tunnels. We hope we can rescue them by tomorrow morning," said Sheikh Mizanur Rahman, deputy director of the Bangladeshi fire service.

Bangladeshi rescuers pulled dozens more people alive from a razed garment factory building Friday as the U.S. pressed for a crackdown on deadly negligence of safety norms in the clothing industry.

The overnight rescue of 45 people provided new hope to thousands of anguished relatives at the scene, on Dhaka's outskirts, but the death toll crept up to 273 as emergency workers battled against the stench of decaying bodies.

Rescuers in Bangladesh Thursday hunted for survivors in a collapsed building as the death toll rose to 159 and criticism mounted of foreign firms that source cheap clothes from the country.

More than 1,000 people were injured when the site housing five garment factories on the outskirts of Dhaka imploded on Wednesday, allegedly after managers ignored workers' warnings that the building had become unstable.

At least 82 people have died and 700 are injured after a eight-storey building housing several garment factories collapsed on the outskirts of Bangladesh's capital on Wednesday, a doctor said.

Hiralal Roy, a senior emergency ward doctor at the nearby Enam hospital where victims are being transferred, told Agence France Presse: "The death toll is now 82. At least 700 people have also been treated at the hospital."

Thousands of members of a hardline Muslim group are rallying in Bangladesh's capital to demand authorities enact an anti-blasphemy law punishing people who insult Islam.

Saturday's rally is taking place amid heightened security in Dhaka and elsewhere after the Hifazat-e-Islam members targeted a group of bloggers who they say are atheists. The bloggers, who deny they're atheists, are seeking capital punishment for those found guilty of war crimes during the nation's 1971 independence war and also want a ban on Jamaat-e-Islami, the country's largest Islamic party.