Fifteen people were known to have died by last night, 400 were missing and many hundreds injured after a huge fire devoured the shanty homes of tens of thousands of Rohingya in the world's biggest refugee settlement in Bangladesh.

Nearly one million of the persecuted minority - many escaped a 2017 military crackdown in Myanmar that UN investigators concluded had "genocidal intent" - live in squalid conditions in a network of camps in the Cox's Bazar district.

The fire left at least 50,000 people homeless as it ripped through bamboo-and-tarpaulin shelters.

Families fled with whatever they could carry, with parents separated from children in the rush. "People ran for their lives as it spread fast," a refugee said. "Many were injured and I saw at least four bodies."

It was the third blaze in four days but the biggest of many since 2017, and Bangladeshi officials ordered a probe.

Authorities said the blaze appeared to have started in one of the 34 camps that span about 3,200 hectares of land before spreading rapidly to three other sites despite efforts by hundreds of firefighters, who brought the blaze under control around midnight on Monday.

Police inspector Gazi Salahuddin said the fire grew as cooking gas cylinders exploded.

Refugees International said that many children were missing, and some were unable to flee because of barbed wire set up in the camps. This was echoed by Myo Min Khan, a Rohingya, who said: "We were unable to flee because of the fence, and my youngest daughter got badly injured."

The UN's International Organization for Migration pledged US$1 million (HK$7.8 million) for relief efforts, but US$20 million more was needed.

Officials ordered a probe into the fire that burned down shelters in Cox's Bazar. REUTERS

Deadly blaze devours Rohingya shanty sprawl