Twenty-seven of Assam's 33 districts have been hit by landslides and overflowing rivers since the beginning of this week, according to the Assam State Disaster Management Authority (ASDMA).
Disaster response forces used boats and helicopters to rescue nearly 7,500 people on Thursday.
“We have a death toll of nine including victims of flood and landslides. About 85,000 people are shifted to 172 relief camps. We are ensuring people remain safe and their health is taken care of,” Gyanendra Dev Tripathi, chief executive of ASDMA, told The National.
“Reconstruction and relief operations are continuing with the help of disaster forces,” he said.
Houses were swept away, roads and railways lines damaged and tunnels blocked with debris. Thousands of hectares of cropland are under flood water.
The worst hit region is Nagaon district where more than 300,000 people were left homeless by the flooding.
“Our land is gone. We are eating only one meal a day and we don't have resources to move somewhere else. We are waiting for government help,” Lilabati Das,” 41, whose mud hut was washed away in the flood, told a local television channel.
In Dima Hasao district, Mr Tripathi said 100 kilometres of national motorway and a railway line were damaged, disrupting the delivery of basic supplies to stranded people.
Air Force sorties were delivering essential supplies o those trapped and airlifting the marooned.
“Houses have been lost, crops have been lost … the highway and the railway is the lifeline but we have been facing the biggest challenge to provide basic supplies such as food [and] rice. But the silver lining is that some portions are being restored and opened with the help of relief workers,” Mr Tripathi said.
Assam routinely suffers from annual floods but in recent years, deluges have caused widespread havoc.
Authorities have built 40 artificial highlands in Kaziranga National Park, a Unesco world heritage site and home to one-horned rhinoceros, and other wildlife sanctuaries to provide refuge to the stranded animals during the floods.
In neighbouring Arunachal Pradesh, incessant rains have triggered landslides in various parts of the state, closing many roads.
The India Meteorological Department has predicted another spell of heavy rains in the state on Saturday.
The weather office also issued a “yellow alert” in southern coastal Kerala state for the weekend.
The state has endured heavy rainfall for the past few days as a result of the Southwest Monsoon season, when the whole country receives about 75 per cent of its rainfall during this period.