Flash floods and landslides triggered by heavy monsoon rains in northeast India have claimed at least 26 lives and another eight people are missing, a report said on Sunday.

India's army and air force launched rescue operations in areas badly hit by the rains that have been lashing the states of Sikkim, Assam and Arunachal Pradesh for days, the Press Trust of India said.

In a remote area of north Sikkim, at least 21 bodies, including those of members of the Indo-Tibetan Border Police, had been found while eight other people were missing, the news agency said.

In Assam, five deaths were reported in widespread flooding that submerged a major wildlife sanctuary and parks, the news agency said.

The rains have swollen the mighty Brahmaputra river and its tributaries, causing floods that have affected hundreds of thousands of people in the region, the report said.

The air force was dropping food supplies to people marooned by floods.

India's northeast has been especially hard hit by devastating rains during the monsoon, which runs from June to September.