Assam's flood control minister, Nurzamal Sarkar, said the state was on "full alert but one can't stop the floods from causing devastation."

Some 520,000 tribals in the Dhemaji district, normally worst hit by the annual flooding, seek to survive the high waters by staying aboard the boats and bamboo rafts they usually use for fishing.

"Last year our family spent 16 days, eating and sleeping on our wooden boat," Mantu Das, a resident of the district, 485 kilometres (300 miles) east of Assam's main city of Guwahati, said.

"Life is very hard during the floods with the rain and storms lashing. Survival becomes a real test."

The 2,906-km (1,801-mile) long Brahmaputra is one of Asia's largest rivers and runs through Tibet, India and Bangladesh before flowing into the Bay of Bengal.

Every year the floods leave a trail of destruction, washing away villages, submerging paddy fields, drowning livestock, besides causing loss of human life and property in the remote state of 26 million.

Last year, officials said some 170 people died and countless others were left homeless in Assam during the floods.

So far there have been two weeks of rain and the weather office has forecast more to come.

"All hell will break loose soon as the level of the river and its tributaries rises every day," Gobind Pegu, 46, told AFP as he repaired his boat.

Equally worried were nearly 150,000 residents of Majuli, the world's largest river island.

The island once covered 1,500 square kilometres (579 miles) and is dotted with Hindu monasteries. But today it is reduced to half its original size due to flooding and erosion.

"The island is on the verge of extinction with its landmass decreasing by the day with the Brahmaputra triggering heavy erosion," geographer Ananda Hazarika said.