The identities of the deceased could not be confirmed yet.
The bus which was carrying extra passengers veered off the road and fell into a roadside pond, leaving three people dead on the spot around 11:30 pm, said Pirgachha Police Station Officer-in-Charge (OC) Nure Alam Siddiqui
He said the injured were taken to Rangpur Medical College Hospital (RMCH) for treatment.
The accident occurred when the victims were returning from a post-wedding reception.
Witnesses said the bus was carrying 50 to 70 Hindu community members from the Najirerhat area of Rangpur City Corporation to a post-wedding feast in Beltoli area of Sundarganj upazila in Gaibandha district.
The accident took place on the return journey near Jabbar's shop in Beltola Bazar on the Pirgachha-Sundarganj regional highway, reports UNB.
Pirgachha Fire Service and police rushed to the spot and began rescue operations with the help of locals.