Aug. 5 (Bloomberg) -- Monsoon rain-driven floods swept across northeastern India, Bangladesh and Nepal, leaving millions of people stranded as the seasonal rainfall began making its way southward.

Estimates of those left homeless varied, with Agence-France Presse reporting 25 million people across the region were forced to flee and that more than 1,400 died. In Bangladesh, more than 100 people died and the toll may reach 500, Saiful Hossian, a spokesman for the Bangladesh Flood Forecasting and Warning Centre, said today in a telephone interview.

The monsoon trough was shifting southward, India Weather Watch said on its Web site yesterday, with heavy rainfall forecast over West Bengal, Orissa and Andhra Pradesh states the next three days.

South Asia usually experiences monsoon rains from June to September, which are vital for the region's agriculture, though they frequently also cause flooding and landslides that devastate crops, destroy homes and trigger diseases such as diarrhea and dysentery.

``We are already talking about more than 20 million people displaced and living through one of the worst nightmares,'' P.V. Unnikrishnan, coordinator of relief operations in Bangladesh and India for ActionAid International, a non-governmental organization, said today in a telephone interview from Bangalore.

Unprecedented Rainfall

In India, about 1,103 people had died, the United Nations Children's Fund, Unicef, said Aug. 3 on its Web site.

``The rainfall is unprecedented and the extent of the damage is high,'' Manoj Srivastava, disaster management chief for Bihar, India's second-most populous state and one of the hardest hit, said today in a telephone interview. ``Relief efforts, which have been hampered by submerged roads and difficulty in communications, are now in full swing.''

It is ``the worst flooding in living memory,'' Unicef said. ``The sheer size and scale of the flooding and the massive numbers of people affected pose an unprecedented challenge to the delivery of desperately needed humanitarian assistance.''

Indian Air Force helicopters started dropping food packages yesterday, the Press Trust of India reported.

``We plan to drop 30 tons of dry rations today in areas which were cut off, such as Darbangha and Madhubani in Bihar, using four helicopters,'' Srivastava said. ``Now that the water is receding, we are speeding up relief efforts.''

Danger Level

``In Bihar, 10 million people have been affected,'' Gopal Prasad Singh, deputy secretary in the Disaster Management Cell, said today in a telephone interview from the capital, Patna. ``The death toll is 64 and may rise. Rivers are still flowing above the danger level.''

In India's northeastern Assam state, about 6 million people, a quarter of its population, have been displaced by floods, Somnath Basu, who is coordinating relief operations for Unicef, said in a telephone interview from state capital Guwahati. Railway services were suspended and flood waters washed away highways, AP said, citing state government officials.

``The flood situation was very critical two days ago, but it's receding now,'' Bhumidhar Barman, a minister in the state government of Assam, said today in a telephone interview. ``Damage is extensive, as out of the 27 districts, 24 were under water. Rescue operations are being carried out and some of the homeless are now residing in camps.''

The death toll in Assam has risen to 24, although rainfall has decreased over the past 24 hours,'' Rupak Kumar Majzumdar, deputy secretary of the Relief and Disaster Management Department in Assam, said today in a telephone interview.

Troops Deployed

Indian authorities deployed troops to help evacuate people in the worst-hit areas, including northern Uttar Pradesh state, AP said.

About 2.5 million people have been affected by floods in Uttar Pradesh, Umesh Sinha, Relief Commissioner of Uttar Pradesh, said in a telephone interview from the capital city of Lucknow. About 1,700 government relief officials and 200 soldiers were making rescue efforts, Sinha said, adding 125 people died in the state due to drowning, house collapses and snake bites.

Boats and helicopters have been deployed to help families in the 2,400 villages affected. This year, the rains came in too early and some of the districts got more rainfall in a week than they usually receive in a year, Sinha said.

In Bangladesh, a low-lying delta nation of 145 million people, about 5 million were displaced or marooned after rivers burst their banks, the Associated Press reported yesterday.

``We expect the death toll to be in the region of about 500 and more once the water recedes, because cholera and other water- borne diseases will claim more lives,'' said Hossian, of Bangladesh's Flood Forecasting and Warning Centre. ``People are living on the riverbanks and their health conditions are bad. Many are poor and have nothing to eat.''

In Nepal, relief work was going on and ``there are 74 people reported dead,'' Nepal's Chief Secretary of the Government Bhojraj Ghimire said today in a telephone interview from Kathmandu. ``The toll may go up.''

To contact the reporter on this story: Jay Shankar in Bangalore at jshankar1@bloomberg.net. Katherine Espina in Singapore at kespina@bloomberg.net

Last Updated: August 5, 2007 07:17 EDT