Chief Minister Nitish Kumar has decsribed the situation as a catastrophe and appealed to the Centre for help.
Over 32 lakh people have been left homeless, with the floods affecting 15 of the state's 38 districts.
During his visit to the flood-hit areas in the state on Thursday, Prime Minister Manmohan Singh described the floods as a national calamity and announced the immediate release of Rs 1,000-crore flood relief for Bihar.
Image: Villagers are transported in army boats following their rescue from floodwaters in Sursur area in Araria district.
Photographs: Diptendu Dutta/AFP/Getty Images
Also read: Floods: Bihar will take years to recover