The United Nations said meanwhile it would seek $430 million to increase operations in the camps along the Bangladesh-Myanmar border. The Rohingya Muslims have poured across the frontier to escape a military crackdown in Buddhist-majority Myanmar.
A 20-bed treatment clinic was opened at Kutupalong refugee camp Monday to treat diarrhoea victims and another 60-bed facility would be set up this week, a UN spokesman said, AFP reported.
UN staff and volunteers were touring Kutupalong and nearby makeshift camps to identify those who have not sought treatment, UN refugee agency spokesman Andrej Mahecic said.
"We have seen an increasing trend of diarrhoeal disease cases, including cases of diarrhoea with severe dehydration," he said.
Bangladesh authorities were not aware of diarrhoea-related deaths in the camps, but the health department said more than 10,500 Rohingya had been treated since the influx began on Aug. 25.
Last week the World Health Organization warned of a growing cholera risk in the makeshift camps as they lacked safe drinking and hygiene facilities. The Doctors without Borders (MSF) group also said the camps were on the brink of a public health disaster.
The camps face dire shortages of food and medicine in what has become one of the world's largest refugee settlements.
The overwhelmed camps around the border town of Cox's Bazar already had 300,000 people who fled earlier violence in Myanmar's Rakhine state.
Mark Lowcock, a UN undersecretary general for humanitarian affairs, said the world body would be seeking "something like $430 million to enable us to scale up the relief operation."
"Conditions in the camps at the moment are terrible," Lowcock told reporters in Cox's Bazar.
The UN has already given an extra $12 million from its emergency response fund.
"What we want to do is to make sure that the tragedy of the Rohingya is not magnified and amplified by a human catastrophe and health catastrophe," the UN official declared.