The deceased include an eight-year old girl and a 40-year-old man.
All the people were coming from Uttar Pradesh to participate in a marriage ceremony at the house of Gopalganj Zila Parishad Chairperson Chanda Singh.
"All the persons were traveling in a SUV. It seems the driver lost his balance and the vehicle turned turtle after skidding off the road," said ASP Anil Kumar.
Acting quickly, the police personnel put the injured in an ambulance and got them admitted at an hospital in the close by town of Deoria in Uttar Pradesh for better treatment.