Severe floods caused by monsoon rains have forced over two million people to flee their homes in north-east India and Bangladesh, officials say.
Bad weather has hindered rescue operations
About 40 people are feared dead in India after the Brahmaputra river broke its banks - thousands are cut off.
A third of Bangladesh has been affected, with three million people marooned, thousands more searching for shelter and several people killed.
In Nepal, flash floods have killed at least 36 people in the past week.
'Worst in a decade'
Hundreds of people died last year in South Asia in floods and landslides which are common during the monsoon season.
But officials in Indian and Bangladesh say that this year's flooding is the worst they have seen in over a decade.
"Some 400,000 houses were damaged in floods in 18 of the state's 24 districts," the chief minister of the Indian state of Assam, Tarun Gogoi, told AFP news agency.
"The approximate loss caused by the floods is estimated at about 10 billion rupees ($220m)."
Across South Asia many people have been forced to seek shelter on roof tops, uncertain when they will next be able to get food supplies. They are also at risk from water-borne diseases and snakes desperate to escape the floodwater.
Assam is the worst-affected area in India, where there have been at least 13 recent flood-related deaths, the authorities say.
Emergency officials say bad weather and a shortage of boats are hindering rescue operations.
The floods have also affected more than two million people in the northern Indian state of Bihar where
at least 25 people have been killed and four out of 13 districts are severely affected.
Hundreds of army and paramilitary forces are taking part in the relief operation there, and officials say that road and train links have been totally destroyed.
A BBC correspondent in Bihar says that thousands of people have taken shelter near railway stations as relief teams continue to airdrop food and emergency medicines.
In Bangladesh, the north-east has been the worst affected with three million people marooned and thousands of others cut off from their villages and searching for shelter.
Parts of the city of Sylhet - cut off from the rest of the country - are knee deep in water.
Officials in Sylhet says the flooding is the worst since 1988, when two-thirds of the country was submerged.
The Flood Forecasting and Warning Centre in the capital, Dhaka, says the worst is yet to come, with more low-lying areas of the country likely to be severely flooded.
Local officials say two people were electrocuted in Sylhet when cables came into contact with the flood waters.
Several other people are reported to have drowned when their boat capsized.
"The villages in Sunamganj districts [in Sylhet division] are like islands in a sea, completely surrounded by water," police official Abdus Salam Khan told AFP.
Forecasters are predicting more rain in the coming days and say the rising waters could begin to affect the area around the capital.
In Nepal, landslides caused by the rain have also blocked major roads into the capital, Kathmandu, cutting it off from other parts of the country.
Thousands of people have been displaced across the kingdom and many farms have been inundated.
The south and east are said to be worst hit, and at least 46 people are reported to have been killed.