Latest available Indian government figures cited by Unicef say that over 1,100 people have died in this year's monsoon.
As many as 10 million people have been displaced in Bihar alone.
Another 5.5 million were displaced in Assam, with a further 1.4 million displaced in Uttar Pradesh, officials have said, with heavy rains expected to continue.
|Displaced Indian villagers have been taking|
refuge in schools [AFP]
Violence flared on Saturday in Bihar when police tried to move hungry, homeless people away from an elevated train track to be able to dig a ditch and drain floodwaters from a nearby village.
One person was killed and more than 20 wounded in clashes there, officials and witnesses said.
State officials raised the death toll there by 20 to 77.
Health workers and aid groups in Assam began to treat and feed the displaced with limited medicines and supplies.
Elsewhere, villagers were getting desperate and hungry.
Many people were suffering from diarrhoea, dysentery and fever. Officials have warned of outbreaks of malaria.
In Bangladesh, at least 16 people, including six children, drowned overnight taking the country's death toll to at least 81, an official at the government's flood monitoring agency has said.
The floods have spread to 41 of Bangladesh's 64 districts.
Parts of Dhaka are under water and more areas might flood in the next few days.
In Nepal, the UN has said that rains over the last few weeks had triggered floods and landslides in both the west and east that have killed 84 and displaced 270,000 people.
The Nepalese army and rafting companies - used to taking tourists - have joined rescue operations.