Relief teams across South Asia are struggling to reach over 10 million people hit by severe monsoon flooding.
A woman takes her son to safety in Assam
Large parts of north-east India, Nepal and Bangladesh are under water - scores of people have died in recent days.
Rescue workers are using boats and helicopters to ferry supplies to those cut off, many of whom have been on their roofs for days.
Hundreds of kilometres of roads and railways have been swept away or submerged, hampering relief efforts.
Floods and landslides are common in South Asia during the monsoon season when annual rains combine with melting snow from the Himalayas.
Bihar and Assam
Officials in India's Bihar state, among the worst-hit areas, said helicopter pilots were finding it difficult to find those cut off.
More than four million people are affected in Bihar, the authorities say, and about 50 have died in the flooding.
A BBC correspondent in the area says hundreds of villages in the state's north are completely submerged - many people are resorting to eating animal feed. Snakebites are another hazard.
An emergency was declared in the state's Khagaria district on Wednesday after a dam burst on the Bagmati river, submerging three villages.
In Assam state officials say the floods are the most severe in recent memory.
A breach in a dam in neighbouring Bhutan led to rivers flowing into the state bursting their banks.
More than 2.5 million people are homeless, and over 50 are reported to have lost their lives in recent days in Assam.
"I have lost my house and all my belongings - my livelihood as well," one farmer near the state capital, Guwahati, told Reuters news agency.
On Wednesday, the Brahmaputra broke its banks at several points in Guwahati itself, local officials said.
The authorities say they need tents, drinking water and food, as well as medical help.
"There is a fear of an outbreak of epidemics," said Renuka Devi Brakataky, head of Assam's Red Cross.
Further south in Bangladesh, the situation has been worsening as water flows downstream.
The word 'monsoon' comes from the Arabic for 'season'
Describes seasonal reversals of wind direction
From April heat builds over South Asia, creating low pressure areas
Brings moisture-rich south-west winds in from the ocean
The annual rains have swollen South Asia's largest rivers - the Ganges, Brahmaputra and Jamuna - which all flow through Bangladesh before draining into the Bay of Bengal.
Twenty-five of the country's 64 districts are severely affected, the Bangladesh Flood Forecasting and Warning Centre said on Wednesday.
Later in the day, it said the situation had improved slightly in the country's north but was getting worse around the capital, Dhaka.
Authorities say 12 people have been killed so far, and more than three million people are stranded. Thousands of others are homeless and seeking shelter.
Officials in the city of Sylhet - cut off from the rest of the country - say the flooding is the worst since 1988, when two-thirds of Bangladesh was submerged.
In Nepal, meanwhile, the floods have started receding after a week of heavy rain.
At least 50 people died in the kingdom over the last week in landslides and flash floods, and thousands of others have been displaced.
People's homes have been ruined
"We expect the death toll to be much higher than that as
reports could take as much as a week to reach us," an emergency official told the Associated Press.
While parts of South Asia have had too much rain, some areas in central and northern India are desperate for it to avoid drought.
India was hit by a massive drought in 2002 and officials say that they want to be better prepared this time.
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