Nearly two million people have been affected by the floods in Bihar, including thousands who have been forced to evacuate from their homes, officials said on Monday.
Over one million people were affected in the worst-hit districts of Kishanganj, Araria, Purnea and Katihar in last two days.
"Thousands were displaced after their villages were inundated," a Kishanganj district official said.
Other affected districts are Darbhanga, Madhubani, Sitamarhi, Madhepura, Saharsa, Supaul, East and West Champaran.
Railway stations in Kishanganj, Katihar and Jogbani in Araria were flooded by water, leaving scores of passengers stranded. Eighteen trains have been cancelled since Sunday.
According to officials, crops worth crores were damaged and road link to several places had been snapped.
The state disaster management department has asked people living in low lying areas to move to higher places as heavy rains continued.
"The flood situation in Bihar will continue to be grim following rising water levels in rivers and incessant rains," department officials said.
So far, at least 10 persons, including women and children, have been killed in the floods.
Major rivers in the state including the Koshi, Mahananda, Gandak, Bagmati and Ganga are in spate, officials said.
"With heavy rainfall in the catchment areas in Nepal, the water level of these rivers has been rising for several days," one officer told IANS.
Chief Minister Nitish Kumar on Sunday has sought the Army and the Indian Air Force's help in relief and rescue of affected people.
He also requested Prime Minister Narendra Modi and Union Home Minister Rajnath Singh to provide all possible aid.
"Both have assured their assistance," Nitish Kumar said.
The Chief Minister's Office said an 80-member team from the Bihar Regiment rushed to Kishanganj and Araria on Sunday evening to rescue people.
"Nitish Kumar has also sought 10 additional teams of the National Disaster Relief Fund from the Centre for affected districts."