More than 250,000 people displaced by floods in the Indian state of Bihar could spend up to six months in temporary camps.
The camps will be kept open until flood waters recede, Bihar’s chief minister, Nitish Kumar, says.
Floods have also displaced thousands in India’s Assam state and in Bangladesh.
Hundreds of thousands of people forced from their homes by the disaster are at risk of disease and starvation, according to aid agencies.
The agencies say conditions in relief camps in Bihar are cramped and unhygienic and hundreds of cases of diarrhoea, pneumonia and fever have already been reported.
Doctors in the camps have begun immunising flood victims in the hope of countering the spread of disease.
Aid agencies also warn that the number of those killed may rise as receding flood waters wash more bodies ashore.
The floods in Bihar began on 18 August when monsoon rains caused the Kosi river to break its eastern bank in Nepal, where the river is often called the Saptakoshi.
The river’s flow is regulated by a barrage on the Nepalese side of the border which was built in the late 1950s.
Bihar’s Chief Minister Nitish Kumar says the flood victims will need to be supported for up to six months as the flood waters are unlikely to recede before then.
The rescue mission to evacuate those stranded has been called off but thousands of people have refused to leave their homes while some others have begun to return to their villages.
The government has been trying to persuade them to stay away.
In the Indian state of Assam, meanwhile, 19 of 27 districts have been flooded after the Brahmaputra river burst its banks.
Some 1.5m people have been displaced in the state, a local emergency official told AFP news agency.
In Bangladesh, flood waters have continued to rise as a result of heavy rains.
One-third of the country’s districts have been affected by the floods and some 200,000 people have been displaced.
SHAHRUL PESHAWAR – We have to help them