Breaching a 10-year-old record, the Ganga waters entered main roads in Varanasi, forcing people to abandon their homes and move to safer locations.
Boats have become the only mode of transportation in many parts of the temple town.
Along with Varanasi, three other districts — Allahabad, Mirzapur and Ballia — have been affected badly by the floods. As many as 15 of Uttar Pradesh's 75 districts have been hit by floods.
IG (law and order) RK Vishwakarma said the state government received emergency messages from district magistrates of Allahabad, Varanasi, Mirzapur and Ballia. Hundreds of villages in the four districts have been flooded, rendering many people homeless. The administration has started shifting people trapped in marooned villages to safe spots.
Administration officers said 200,000 people have been affected and 6,000 people have been shifted to relief camps. On Monday, 175 villages were flooded.
The UP government has rushed the flood company of the Provincial Armed Constabulary to carry out relief and rescue work in the four affected districts. In Allahabad, the army has been put on alert after the spate in the Ganga breached the Bakshi embankment, inundating large areas of the city. One person was swept by river Rapti in Balrampur district, raising the death toll to 236 since the onset of the monsoon.