Raging floodwaters have hit the north west of the country, marooning a million people and causing flash floods and landslides, Christian Aid reports.
The fatalities have occurred largely in the south east of the country, where the Ramu district of Cox's Bazaar has been badly hit.
Out of the area's population of half a million, Christian Aid says that around 450,000 people have been severely affected.
Around 1,000 acres of seasonal crops have been destroyed, and fish hatcheries and poultry farms have also been devastated.
A total of 54,000 households have been reportedly displaced across the north west and south east.
Fresh drinking water, food and fuel are in short supply, and many people have been forced to stay in schools and on roadsides.
Christian Aid said it was "highly likely" that they will face nutritional, health and financial crises in weeks to come.
The development agency is releasing emergency funds to support the work of local partners in the affected areas.
They are providing food parcels including rice, lentils, oil, salt and sugar, and household items, including plastic sheets, soap and oral rehydration salts.
Christian Aid is also working with ACT Alliance in the Assam region of India where families are also fighting for survival following torrential rains.