More than 360 people are now thought to have died in the flooding in India and Bangladesh caused by monsoon rains.
Many Bangladeshis are fleeing to higher ground
Some 14 million people have been displaced in India alone and clashes have been reported over food drops in the worst hit Bihar state.
Aid workers are battling to supply food and water to millions of increasingly desperate flood victims.
However, life in flood-affected southern Nepal is returning to normal after weeks of torrential rains.
Water levels in some north Indian rivers are now receding but food, water and medicine is still not reaching those who need it most.
Clashes were reported over food drops in the worst hit area, India's state of Bihar, where 11 million are affected.
Federal ministers are expected to visit the worst-affected areas to try and assess the damage on Tuesday.
'More resources needed'
Aid agencies have warned of the outbreak of diarrhoea and other water-borne diseases.
Bihar officials have blamed Nepal over the water levels
Bihar's latest victims were in a boat that capsized on the Ganges. Two people are confirmed dead and dozens are missing.
More than 20 million people have been affected across areas of northern India, Bangladesh and Nepal.
Potheri Unnikrishnan, from the humanitarian group Actionaid, said he expected pockets of flooding to continue causing problems for months.
"It is absolutely necessary that everyone - the government, the NGOs and the international community - put more resources to fight this out," he said.
Many villagers have not had supplies for days while rescuers said they had had little rest since the flooding began.
Bhagwan Manjhi from Bihar's East Champaran district told local television: "We are surviving on snails as we have nothing to eat."
Bihar and Nepal have clashed over who is responsible for the water levels.
Officials in Bihar accused Nepal of failing to build dams to control Himalayan water.
But an MP in Nepal, Purna Kumari Subedi, blamed a dam built in India at Laxmanpur, telling AFP that it should be destroyed.
THE ASIAN MONSOON
Monsoon winds blow north-easterly for one half of the year, and from the south-west for the other half
South-westerly winds bring the heavy rains from June to Sept
Winds arrive in southern India six weeks before the north west
Annual rainfall varies considerably
Although rains have generally eased, water levels coming down from Nepal are unlikely to lower soon, officials said.
Levels have lowered in areas such as Assam but officials said they were worried about an outbreak of disease as waters receded and temperatures soared.
Officials in Uttar Pradesh said they expected the situation to get better soon with water in three rivers - the Ghagra, Rapti and Gandak - receding.
In Bangladesh, the UN's World Food Programme has been distributing emergency aid to flood-hit areas.
The agency estimated that one million people had been directly affected and some were in need of urgent assistance.
In Nepal, many roads in the flooded areas have been cut and bridges have been washed away.
It is proving hard for aid agencies and the government to bring help.
They have distributed food supplies to some communities, but many people who are still living in damaged mud and thatched homes complain it is not enough.