At least 11 people have died from diarrhoea in the remote Kurukpata union of Alikadam Upazila in Bandarban as of Wednesday.
More than 50 people have been seriously affected by the disease in the region, said 7-Field Ambulance Bandarban Major Md Saiful Islam.
Three of the critically ill patients were carried by helicopter to Bandarban Sadar Hospital today.
"At the initiative of the Alikadam Army Zone and health department, a field hospital has been set up in the affected area and treatment is on by providing clean water, purification tablets, food saline and necessary medicines," Major Saiful said.
Earlier on Monday, two medical teams from the army and the health department were sent to Kurukpata area after receiving reports of an outbreak of diarrhoea.
Kratpung Mro, chairman of the Kurukpata Union Parishad, said the area is mainly inhabited by the Mro and Tripura communities.
"These areas are inaccessible and completely without mobile network. At this time of the year, the people there are afflicted with water-borne diseases, including diarrhoea, that usually kills one or two people per year. But this time it has spread widely," he added.
District Civil Surgeon Dr Aong Sui Prue Marma said that most people in remote areas use Jhiri and Chhara water for drinking. "When it rains, these waters become polluted. Drinking which causes diarrhoea and water-borne diseases," he said.