Torrential rains in the upper reaches of Arunachal Pradesh, landslides and overflowing rivers have wrecked havoc in India's seven northeastern states in the past two days, killing at least half a dozen people and affecting over 400,000 people.

The Met department has forecast heavy rains in the next 48 hours raising the spectre of another round of flood throughout the Brahmaputra Valley in the coming four days.

The flood situation worsened overnight with the Brahmaputra breaching several mud embankments throughout its 800-km course in Assam.

The Brahmaputra is flowing above the danger level in at least 11 main channels, including Guwahati, inundating several low-lying areas in the capital city.

"The river flowing more than two metres above the danger mark in some areas," a Central Water Commission bulletin on Tuesday said.

An Assam government press note said up to 290,000 people were left homeless since Friday when the second wave of flood began in the state.

Earlier in June about 400,000 people were displaced in the state during the first wave of floods.

The worst affected districts were Dhemaji, Kamrup, Jorhat, Goalpara, Dhubri, Darrang, and Nalbari.

The famed Kaziranga National Park has also been flooded.

Park officials said that large tracts of the Bagori range are submerged. The highest concentration of the animals are found in this range. The 430 square km park has about 1,500 rhinos, according to the latest survey.

Animals have already started to cross over to the adjacent Karbi Anglong hills. Elephants and deer have crossed over to the hills across the National Highway 37, officials said.