At least 30 villages in Fulgazi and Parshuram upazilas of Feni district have been flooded after flood control embankments along the Muhuri, Kuhua and Silonia rivers gave way at 15 points.
Vast areas, including Jangal Ghona, Sahebnagar, Gadanagar and Derpara in Fulgazi, the western parts of Parshuram, and southern Sonagazi, were underwater on Wednesday, with homes, paddy fields, fish farms and roads inundated.
The previous day, the Bangladesh Water Development Board said the Muhuri River was flowing 137 centimetres above the danger level.
Under intense pressure from the current, several weak points of the embankments had given way, it added.
Authorities said they had begun emergency repair work using geo-bags and sand sacks to contain the damage.
However, residents said the situation remained dire, with many people marooned and taking shelter on elevated roads and in school buildings.
Many others, unable to reach official shelters, were spending the nights in the open with their children and livestock.
Locals alleged that the embankments collapsed at the same spots every monsoon, but no permanent solution had been implemented.
