The injured have been admitted to a government hospital.
Train services were disrupted on the Chhapra-Gorakhpur section of the Varanasi rail division.
According to police officials, a railway official, who was posted at the railway crossing, ran away after the accident.
"It appears that the bus driver was trying to cross the tracks ignoring the speeding train because of the absence of the gateman at the railway crossing," a police official said.
Railways Minister C.P. Joshi announced ex-gratia of Rs.5 lakh to the next of kin of each deceased, Rs.1 lakh each to those grievously injured and Rs.25,000 to those who sustained minor injuries in the accident.