New Delhi - The Indian military on Tuesday sent in more soldiers, boats and aircraft to help with rescue and relief efforts in India's flood-devastated eastern state of Bihar amid reports of food riots and warnings of possible outbreaks of waterborne disease.

At least 56 deaths had been confirmed since the Kosi River breached an embankment in neighbouring Nepal and inundated vast areas of Bihar on August 18, and officials estimated that another 50 people had died.

The number of deaths could go up, Prataya Amrit, a senior official at the Bihar Disaster Management Department, warned in the state capital, Patna.

"Six critical areas have been identified," Amrit said by telephone. "The army and navy have moved into these areas to help rescue an estimated 60,000 people."

The air force was air-dropping water, food packets and blankets, he said.

At least 3.5 million people in 16 districts of the state have been affected by the floods, and Amrit said it might take a couple of days before evacuations could be completed.

He said more than 200,000 flood victims were still marooned by floodwaters and needed to be rescued.

At least 600,000 people have already been evacuated and about half of them were being lodged in 193 temporary relief camps set up by the government, Amrit said. He said several non-governmental organizations had also set up camps and many families had moved in with relatives and friends.

Aid workers warned that conditions in the relief camps were difficult with overcrowding and shortages of doctors, medicine and essential supplies.

Thousands of people remained stranded on small outcrops of land that stood above floodwaters, on trees and on top of flooded buildings. They have been without food for days and were drinking filthy water, local media reports said.

A United Nations statement has warned that limited supplies of safe drinking water and poor hygiene in the flooded areas posed a great risk of water- and parasite-borne diseases.

The Indian Army, which had deployed at least 5,000 troopers earlier in the week, deployed an additional 3,000 Tuesday, to help in rescue and relief operations.

Local administrations in the flooded districts were in disarray, the NDTV television channel reported.

There were reports of food riots from inundated Madhepura district, where desperate people asked to wait in queues looted a depot storing food packets, NDTV reported.

State governments, federal institutions and corporations announced contributions to flood relief. India's federal Reserve Bank said "consumption loans" would be provided to all flood victims.

The National Disaster Management Division said the Kosi continued to flow above danger levels at several places along with the Ganga and several other rivers in the state.

Prime Minister Manmohan Singh earlier described the situation as a "national calamity" and announced a relief package of 234 million dollars.

A total of 1,746 people have died this year across India in floods brought on by annual monsoon rains that last from June to September. (dpa)