Five prison officers have been injured in an attack by an inmate.
The attack happened at HMP Bristol on Friday afternoon and all five officers “received hospital treatment”, a Prison Service spokeswoman said.
Sarah Rigby, from the Prison Officers Association (POA), said the prisoner had been transferred from a high-security jail.
The Prison Service said it was investing in staff safety by issuing body-worn cameras and pepper spray.
Ms Rigby said the inmate “should never have been moved out of the high-security establishment”.
She said the injured staff were “now out of hospital and are recovering at home. Our thoughts are with them and we can only hope they make a full recovery”.
HMP Bristol currently has about 520 adult male prisoners and a limited number of young offenders, both convicted and on remand from local courts.
It is a local category B prison with the majority of prisoners staying for less than 12 months.