The wire snapped and fell on the bus while it was leaving Jahanabad bus station this afternoon, police said.
Hearing cries of the passengers local villagers reached the spot and rescued at least 12 of them by smashing windows and breaking doors of the bus, sources said.
Police have confirmed the death of eight persons.
At least 25 people were injured in the incident and were admitted to different hospitals in Fatehpur, Bindki and Kanpur.
Around 50 passengers were travelling in the bus, sources said.
Senior officials, including District Magistrate Kanchan Verma and Superintendent of Police Rajendra Singh reached the spot where rescue work was being carried out, sources said.
Alleging laxity on part of administration local villagers blocked the road.
Meanwhile, BJP state president Laxmi Kant Bajpai while expressing grief over the incident demanded an ex-gratia to kin to passengers killed in the accident.