Millions of malnourished Indian children are vulnerable to disease after South Asia's worst floods in years, officials and aid groups said on Wednesday, calling for urgent assistance.

|PIC1|Hundreds of UNICEF workers rushed to immunise and supply rehydration fluid sachets to children in the impoverished eastern state of Bihar, where millions are stranded on embankments or living in primitive shelters on highways.

They are exposed to sweltering temperatures, sudden downpours and filthy conditions, making them sitting ducks for infections. Hundreds of children have already caught diarrhoea, reports say.

The latest bout of monsoon flooding, which began about three weeks ago, is said to be the worst in living memory in parts of Bihar. It has affected about 30 million people across India, 10 million of them in densely populated Bihar alone.

On Wednesday, fresh flooding was reported from the eastern state of Orissa and the western state of Gujarat, where six people were killed following heavy rains over the last two days, officials said.

Another 20 million people in neighbouring Bangladesh are coping with flood waters that have swamped more than half of the low-lying, riverine nation.

UN Secretary-General Ban Ki-moon said in a statement he was worried about the "economic devastation" faced by flood victims. But he praised what he called a "prompt and effective" response, adding that the UN remained ready to help.

In Bihar, children were seen running down embankments to grab food sacks dropped by occasional helicopter sorties. But they lost out to the adults and often returned empty-handed and bewildered as the aircraft pulled away.

"In the big scramble for relief, kids and women are not prioritised and we need to focus on them, especially where malnutrition is high," said Marzio Babille, head of health for UNICEF in India.

"ENDLESS WAIT FOR HELP"

Five-year-old Kanti Kumari sat outside a makeshift shelter of bamboo canes and a black plastic sheet and wished she could go back to her sturdier thatched home, seen submerged in the distance in Bochaha village. "My ear hurts," said the skinny girl whose face was smudged with dirt. "I feel hungry often."

Her mother Sheila Devi said no doctor or health worker had visited her family of six daughters and rickshaw-puller husband, despite the fact they lived by the side of a pot-holed national highway where trucks regularly ply.

Nor have they received food, and school is not an option.

"They barely can get anything to eat. How can we even think of school," said Devi, holding her two-month-old baby, whose face was marked by rashes.

About 545 people have been killed in the floods, including 192 in Bangladesh which reported 28 new deaths on Wednesday, mostly by drowning, disease and snakebites.

More than 50,000 people were suffering from diarrhoea in the flood-hit districts of Bangladesh and many more were sick with other waterborne diseases, authorities said. More than 400,000 people had taken shelter in relief centres.

"We hate to sit idle or rely on doles for a living. But the cruel floods have made us jobless," said Fahima Begum of Jasaldia village, about an hour by road from the Bangladeshi capital of Dhaka.

"I am trying to keep my children alive, at least," Fahima said as her son and two daughters sipped a potful of gruel.

India's Bihar, home to about 90 million people, is one of the country's poorest and most lawless states. Nearly 60 percent of its young children are malnourished, far higher than the 46 percent average nationally.

Officials said caring for millions of flood-hit children was daunting as hundreds of primary health centres (PHCs) -- the first point of healthcare in rural India -- had been flooded.

UNICEF said millions could fall sick with malaria, dengue fever and other diseases if authorities did not bring food and medicine within days to those stranded.