The Indian army and navy stepped up efforts on Monday to rescue hundreds of thousands of people marooned by floods, while rising river levels also rang alarm bells in neighbouring Bangladesh.
In India's impoverished eastern state of Bihar, villagers have been living on rooftops for days, while others are eating plants and leaves after exhausting food stocks.
Aid agencies said the Bihar government should have done more to anticipate the disaster and plan relief operations in a region hit by monsoon flooding every year.
Three million people have been displaced from their homes and at least 90 killed by floods in Bihar, officials say, after the Kosi river burst a dam in Nepal in August, swamping hundreds of villages in Bihar and destroying 100,000 hectares of farmlands.
Since the monsoon began in South Asia in June, more than 1,000 people have died in floods, with most of the casualties recorded in India's northern state of Uttar Pradesh in July.
In Bihar, hundreds of boats are being used to evacuate people but more are needed, while heavy rains over the past few days have hampered rescue and relief operations, officials said.
The army, which had already deployed five columns of around 120 men, sent in another 14 to help with rescue efforts and to restore order, officials said on Monday. Three naval companies were also asked to help.
More than 467,000 people have been evacuated so far, but there are thousands still marooned. Activists and local media say the death toll could be many times higher than official estimates.
In India's northeastern state of Assam, rising rivers broke mud embankments and swamped more than 100 villages, forcing 50,000 people from their homes. Two people drowned overnight, raising the death toll in the northeast region to 34.
Authorities said at least 400,000 people were living in knee-deep water in villages along the border with Bangladesh.
Bangladesh, Nepal affected
In Bangladesh, about 500,000 people were marooned after several rivers in the north and central districts broke their banks and swamped villages and farmlands.
The Flood Forecasting Centre warned the flood situation could worsen in the next couple of days as the country's three major rivers were rising alarmingly. Many schools were closed and turned into relief camps.
Tens of thousands of people have also been displaced in neighbouring Nepal where some of those who have lost their homes are camping under plastic sheets.
Officials say hundreds of people there have been hit by illnesses such as diarrhoea and pneumonia and an estimated 50,000 are homeless.