By PP Singh BBC correspondent in Hajo, Assam

Flood hit Assamese people have lengthy waits for the relief effort

It is only by air that the full scale of the devastation caused by flooding in India's north-eastern state of Assam can be measured.

Everywhere villages and towns are surrounded by water and normally placid rivers have become raging torrents.

At least 25 people have been killed in Assam and five million have been severely affected by floodwaters of the Brahmaputra and its tributaries.

Thousands of people along with their cattle had to stay on roof tops until official help reached them.

Some had to wait many hours, braving the danger of snakes and water borne diseases for the relief effort to arrive.

Marooned people

The delay was lengthy because the flood waters had damaged bridges and overflowed onto roads.

Babul Deka, a resident of Hajo, spent the night on top of his roof along with his family and cattle only to see the waters rising.

For the first 24 hours he and other residents of the area were completely cut off and left to fend for themselves with limited supplies of food and fresh drinking water.

Roads and bridges in parts of the state have been washed away

Deputy Commissioner Samir Sinha told BBC News Online that army speed boats and helicopters from the Indian Air Force (IAF) were being used to reach marooned people and provide them with shelter, medicines and food.

Hundreds have nowhere to cook and are forced to spend the night on embankments.

Local officials with the help of the IAF managed to evacuate nearly 300 school children when helicopter pilots skilfully landed their machines in knee-deep waters.

'Extremely tough'

"It was a great risk to land the helicopters in fast flowing water," Squadron Leader Pande told me, "but then so many children depended on it."

Rafique Mia's eyes brighten up as he sees the helicopters: he is so pleased to see them because the last few days have been extremely tough.

The relief effort has been aided by the Indian Air Force

"I work for the security forces," he said, "but have been stuck here while on leave.

"Before I return to my unit the major task I face is to repair my family's house."

Assam's Deputy Revenue Secretary SR Islam said that 23 out of Assam's 27 districts have been hit by the flooding with 690,000 hectares of land under water.

'People not prepared'

It is estimated that around 468,000 hectares of agricultural land is under water, while around 400,000 houses have been fully or partially damaged.

The state government has set up nearly 1,500 camps on high-rise areas to provide temporary shelter to thousands of people.

The state government has set up nearly 1500 camps on high-rise areas

Assam Chief Minister Tarun Gogoi told the BBC that the flooding is much more serious than in previous years because it has hit areas which are not normally affected, such as the districts of Kamrup, Nalbari, Barpeta and Bangaigaon.

He said that these people were not prepared for such a disaster, unlike the inhabitants of other areas who are used to floods and have an adequate number of boats to evacuate without outside help.

While the flood has already damaged a large number of embankments the biggest threat hanging over the state government is the likely breach of a flood protection project at Gumi, about 40 kms From Guwahati.