"We are looking for survivors. There is a heavy current in the river and we are facing great difficulties," he said.

"It's very dark, there are no lights and more forces are rushing from Patna," Singh said, adding that most passengers were daily labourers and villagers.

More than 455 people have died in India, Bangladesh and Nepal in the latest phase of the annual monsoon floods, which began two to three weeks ago.

Earlier, one teenager drowned in Bihar's Darbhanga district as he went after food being dropped by helicopter, and dozens of others have been injured in similar scrambles or in fights over dwindling food supplies.

The floods, the worst in living memory in some areas, have affected 35 million people in the region and are being seen by some as a symptom of climate change.

Ten million people have been made homeless or left stranded, and are becoming increasingly desperate as they face food shortages and water-borne diseases even as the waters begin to recede in parts of Nepal and northeast India.

Women and children in a Bihar village clashed over small packets of biscuits being handed out by a local aid organisation, while villagers in another part of the state looted a tractor full of grain, officials said.

"We are surviving on snails as we have nothing to eat," Bhagwan Manjhi of Bihar's East Champaran district told a local news channel.

"The waters have taken everything from me except five cows and some chickens," said Taslima, a mother of four malnourished children who gave only one name, as she sat on the roof of her flooded home in Bangladesh's Munshiganj district.

She had been refusing help from relatives in boats because there was not enough room for her livestock, which floated nearby on a makeshift raft of bamboo and thatch.

"They are my only hope for the future," she said.

THREAT OF EPIDEMICS

While the rains had eased in northern and northeastern India, flood waters were inundating fresh areas in central Bangladesh, including the capital of Dhaka, officials said.

In Bihar's Begusarai district, hundreds of people living in makeshift tarpaulin and bamboo shelters on mud embankments rushed down to a nearby field as a helicopter hovered close to the ground.

Four helicopters were skimming over the north of the state, pushing out thousands of sacks of rice, flour, palm sugar, salt, candles and matches -- but it was clear that demand was outstripping supply.

On one sortie, an emaciated naked boy gestured for the helicopter to release more food, while men argued nearby over the sacks, shoving and pushing.

"I feel sad and sympathy for them," district planning officer Birendra Prasad told a Reuters reporter aboard the helicopter. "At least someone gets something."

UNICEF said it was starting to see early reports of diarrhoea, and urged Bihar's government to drop water pouches instead of rigid containers, which were bursting on impact.

Marzio Babille, who is coordinating the UN response to the Bihar flooding, said he was also worried about diseases such as measles in a state where only a third of children are fully vaccinated and nearly two-thirds are malnourished.

"This population is going to be exposed for two weeks, and even a month," he said. "This is the impact of climate change, and we need new ways of assessing risk."

With floods inundating nearly two-thirds of Bangladesh, 36 more people were drowned or killed by snakebites overnight, taking the confirmed death toll from more than two weeks of deluge to 156, an official said.

In Nepal, where around 60 people have died in the last couple of weeks, hundreds of people were returning to their muddy homes as water levels receded.