More than 60 people are believed dead after a boat carrying Rohingya Muslims fleeing Myanmar capsized, the UN migration agency has said.
The refugees drowned in heavy seas off Bangladesh late on Thursday, part of a new surge of people fleeing a Myanmar army campaign and communal violence that the UN describes as "ethnic cleansing".
US Ambassador to the United Nations Nikki Haley called on countries to ban providing weapons to Myanmar over the violence, Reuters reported.
23 human bodies have been retrieved from the water so far, but the death toll is expected to exceed 60.
"Forty are missing and presumed drowned," IOM spokesman Joel Millman told reporters in Geneva.
Shona Miah, 32, told AFP; "My wife and two boys survived, but I lost my three daughters."
A dire shortage of clean water, toilets and sanitation is spreading disease and pushing the camps to the precipice of a health disaster, the Red Cross warned.
"Our mobile clinics are treating more people, especially children, who are very sick from diarrhoeal diseases which are a direct result of the terrible sanitation conditions," said Mozharul Huq, Secretary-General of the Bangladesh Red Crescent Society.
In some of the camps hundreds of refugees are sharing a single toilet, said Martin Faller, of International Federation of Red Cross and Red Crescent Societies (IFRC).
"The conditions for an outbreak of disease are all present – we have to act now and we have to act at scale," he added.
The World Health Organization has said one of the diseases it is particularly worried about is cholera.