Detective Superintendent Laura Bartley, senior investigating officer, said:"We remain in the early stages of this complex and fast-moving murder investigation. "At this stage of our enquiries, we believe the violent disorder involved members of two rival Outlaw Motorcycle Clubs, the Vikings and the Hells Angels. Gwent Police were called to reports of violent disorder involving a group of men on Mill Street at around 7.15pm. Seven men remain in police custody. Information can be submitted through the Major Incident Public Portal, by calling 101, or by contacting Gwent Police through their website or social media channels.