Floods in India's northeast have killed at least 83 people and led to the death of three rare one-horned rhinoceros at a national park that has the world's largest concentration of the species.

The floods caused by torrential rains across the hilly states of Assam, Arunachal Pradesh, Nagaland and Manipur over the past two weeks, have also triggered landslides.

In all, more than two million people have been displaced, authorities say.

"Assam is the worst hit with 53 lives lost so far in floods and landslides with some 2 million people displaced," Assam Chief Minister Sarbananda Sonowal told Reuters news agency.

"Relief and rescue operations are going on a war footing."

Prime Minister Narendra Modi has sent a team of federal government officials, led by junior home minister Kiren Rijiju, to assess the damage.

The overflowing Brahmaputra River has also completely marooned the Kaziranga wildlife sanctuary in Assam, forcing animals to flee to safer areas.

A one-horned rhinoceros drowned on Friday, taking the toll of the endangered animals in the flooding to three, Assam's forest minister, Pramila Rani Brahma, told Reuters.

The Kaziranga National Park, a UNESCO world heritage site, is home to an estimated 2,500 rhinos out of a world population of some 3,000.

Nearly 60 other animals, mostly deer and wild boars, have been killed in the floods, she said.