Officials say that water levels are coming down
Efforts to rescue flood victims have entered a "final and crucial" stage in the northern Indian state of Bihar, the senior official in charge has said.
Prataya Amrit told the BBC News website that 60,000 to 80,000 people needed to be rescued from "six critical areas" in the districts of Sepaul and Madhepura.
He said more than 650,000 people had been rescued from the affected areas. More than 90 people have died.
Water levels in the flooded areas have come down "drastically", he said.
Meanwhile, monsoon waters have been causing havoc in India's Assam state, as well as in Nepal and Bangladesh.
The authorities in Bihar have been criticised for failing to rescue flood victims well over a week after the scale of the flooding became apparent.
Monsoon rains caused the river Kosi to change course, severely affecting areas not normally prone to floods.
Mr Amrit said that more than 3,000 soldiers, aided by the navy, had rescued most of the stranded people.
"We are looking to complete rescue and evacuation operations over the next two days," he said.
More than 250 relief camps have been set up
"It is the most crucial part of the operation because these are areas which have borne the maximum brunt of the floods."
These areas are in the worst affected districts of Sepaul and Madhepura.
However, a non-governmental organisation (NGO) in Bihar, Mandan Bharti Jagriti Samaj (MBJS), says that 500,000 people still needed to be rescued.
Mr Amrit said that more than 275,000 flood victims had been lodged in more than 250 relief camps in Sepaul, Madhepura, Saharsa and Araria districts.
Tens of thousands of survivors have crowded into unsanitary relief camps, where tensions are growing over the desperate lack of emergency supplies.
There have been reports of flood victims looting relief near some of the camps.
Mr Amrit admitted that there was a problem. "There is a gap between the demand and supply of relief material. We are trying to bridge this gap," he said.
With the numbers of people in the camps expected to nearly double in the coming days, there are fears that poor conditions could lead to outbreaks of diseases such as cholera.
The UN warned that "the heat, combined with limited supplies of safe drinking water and poor hygiene conditions, poses a great risk of water and vector-borne diseases".
The disaster began on 18 August when the Kosi broke 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.
Under a joint agreement India, agreed to pay for the work and be responsible for its maintenance.
Some analysts point out that the structure was built only as a short-term solution, meant to last 20 or 30 years.
Others accuse the Indian government of having failed in its duty to maintain and repair the defences. If they had, they argue, the river could have been kept on course.
Indian engineers say the Nepalese authorities did not give them the safe access they needed to carry out the work and that there were labour problems.
Massive natural silting is also a major problem. Critics say joint efforts to control that silting were also inadequate this year.
In Nepal itself, officials say hundreds of people have been hit by illnesses such as diarrhoea and pneumonia, and an estimated 50,000 are homeless.
They say nearly 1,000 houses have been completely destroyed, and that power supplies and transport have been severely affected.
The costs to the economy are now estimated at one billion Nepalese rupees ($14.25m).