Families who had fled to makeshift camps were forced to scavenge for scarce food in conditions that aid agencies warned would expose thousands to outbreaks of disease.

"I have not eaten for days, give me food," said Babloo, 10, who survived the floods in Bihar by climbing on to his family's buffaloes for hours, crossing submerged villages before reaching a highway. His parents died.

Hungry villagers who remained stranded, including many children, were eating rotten meat and plants to survive. Many feared their homes would be looted if they left.

Flood victims begged for food from passing vehicles as they shouted: "Please stop your car, we want food."

The floods have forced more than three million people from their homes, destroyed 250,000 acres of farmland and killed at least 90 people.

Media reports say the toll is at least 10 times higher, after the Kosi river, which originates in Nepal, burst a dam last month and unleashed the worst flooding in Bihar in 50 years.

"We are appealing to thousands of villagers to leave their houses and come to the camp. It has been raining all day and ... we are afraid these people could get trapped in fresh flooding," Pratyay Amrit, a senior disaster management official, said.

Hungry villagers clashed with camp officials in Madhepura, complaining that they were not getting food.

"The children are hungry, they are crying for food," a sobbing Zubeda Khatoon said.

Authorities in Bihar said on Thursday they have evacuated more than half a million people from flood hit districts.

"There could be thousands missing or still stranded but there is no way we can tell the exact numbers," Amrit said.

On Thursday anxious relatives from nearby states turned up in relief camps.

"I am looking for my little Kishore. Have you seen him?" Zahida Banu, 40, asked camp officials.

While flood waters receded a little in some areas, new areas in Saharsa district and Purnea were flooded this week, forcing hundreds of people to take refuge on an elevated road at night.

"Dear friend, this is perhaps my last message to you, the battery of my mobile phone is low and I am waiting to die as no one has come to rescue me," read a message received by Anupam Bhattacharya of Purnea district.

Officers and soldiers called in by the government to help appeared clueless as there were no administrative officials to guide them in rescue operations.

OVERCROWDED CAMPS

Millions are now living on embankments, roads and in overcrowded camps in filthy conditions, making them extremely vulnerable to infections and water-borne disease in the absence of drinking water, aid agencies say.

Home to 90 million people, Bihar is one of India's poorest states and nearly 56 percent of its young children are malnourished, far higher than the 43 percent average nationally, UNICEF officials said.

In some camps, children were lying near open toilets and cattle saved from floods, making them extremely vulnerable to diseases, aid agencies said.

"We are deeply concerned for children, women and lactating mothers and their needs," Mukesh Puri, a senior UNICEF official coordinating aid operations in Bihar said.

Hundreds of children are already being treated for various illnesses, including diarrhoea, authorities said.

"Many people in my village are sick and hungry, they have given up hope of surviving," said Bindeshwar Rishideb, rescued from flood-hit Madhepura district.