Gunfire erupted at Jamalpur District Jail shortly after 1:30pm on Thursday, spreading panic throughout the city, including the district commissioner's office.
The sound of gunshots continued intermittently for hours, with smoke seen rising from the area. However, details of what caused the incident remain unclear.
Army personnel have surrounded the prison.
Repeated attempts to reach Jail Superintendent Mazharul Islam, who is also serving as the additional duty senior assistant commissioner and executive magistrate, were unsuccessful.
