Fresh flooding left 150,000 homeless in India's West Bengal state, and authorities are struggling to get emergency supplies to cut-off villages.
Eight days of heavy, late-monsoon season rain have forced about 800,000 people from their homes in the densely populated eastern state. Three people have died.
Tens of thousands of mud houses have collapsed or been damaged as major rivers burst their banks, forcing thousands of residents along their banks into hundreds of government flood shelters.
Monsoon flooding in South Asia has killed more than 2,000 people since June and made millions homeless in low-lying eastern India and neighbouring Bangladesh and cost billions of dollars in damage.
Huge tracts of land in Bangladesh have been under water for a week or more after the heaviest downpours in more than half-a-century.
Two UN agencies said today Bangladeshi children and women faced acute malnutrition and without intervention, the number of malnourished children in flood affected areas could rise to one million within six to eight weeks.
The flooding has left 10 million of Bangladesh's 130 million people homeless, and health officials say diarrhoea and pneumonia have killed 350 people, most of them children, and affected 330,000 since mid-July.
The rainy season will end across South Asia from late September.