At least 40 people have been killed and more than 1.5 million displaced due to floods caused by heavy monsoon rains in northeast of India, Reuters reported.

The Brahmaputra river, which flows from China down to India and then through Bangladesh, has burst its banks after torrential monsoon rains, swamping more than 2,500 villages in India's Assam state over the past two weeks. 

Authorities have declared a "maximum health alert" to stop the spread of disease.

Efforts are also underway to help the rhinos and other wildlife put in danger when flood waters swamped the Kaziranga National Park, a UNESCO world heritage site.

"More than 90 percent of the Kaziranga National Park is under water," Assam Forest Minister Pramila Rani Brahma said.