Kabir Ahmed, a 45-year-old villager, said he felt something shake his mud-walled and tin-roof house before a stream of mud and trees came down on top of it.
It was raining when I woke up to say my morning prayers,'' Ahmed said.
"Then there was the jolt followed by rolling mud.''
Ahmed survived when he went out in darkness to see what was happening. Before he could return, his house was covered with tons of mud burying his wife and three young children alive.
The area consists of many hills and forests, allowing for landslides during downpours.
Heavy rain was still pounding Cox's Bazar and nearby districts as well as offshore islands in the Bay of Bengal, officials said.
Low-lying areas have been flooded and communications disrupted, witnesses said.
Landslides hit hillside villages in south and northeastern districts almost every year during the monsoon season.
At least 130 people died in the worst landslide in the port city of Chittagong in June 2007.
In the last few years, Bangladesh, one of the world's poorest and most densely populated countries, has seen an increase in intensity and frequency of climate-related problems.