An attack on five prison guards has been described as “sickening” and “premeditated”.
The officers were taken to hospital after maximum security prisoners allegedly punched and kicked them after being let out of their cells on Monday.
Risdon Prison went into lockdown after the incident, with some of the officers suffering “quite serious injuries”.
Community and Public Sector Union state secretary Tom Lynch said at least one staff member had suffered a broken bone that would require surgery.
“We are talking about serious, criminal assault,” he said.
“I find it quite sickening, there is no excuse.”
Tasmania Police was called to the prison and is now investigating the attack.
Mr Lynch said it was not the first time correctional officers had been subjected to violence at Risdon Prison.
“We have had bad incidents in the past, but things have been reasonably good for a while,” he said.
“The response from the prison has been excellent, they made sure the unit was secured and brought in the tactical response group to make sure there was no further violence.
“We were pleased to hear police were there and charges will be laid, there will be repercussions.”
A Justice Department spokeswoman confirmed the incident had been “initiated by a non-compliant prisoner”.
“Five Tasmania Prison Service staff were taken to hospital as a precaution,” they said.
“The incident was quickly resolved and the prison has returned to normal operations.”
The union plans to discuss the incident further with the department.
“This needs to be taken very seriously,” Mr Lynch said.
“There are learnings from this, about the way the unit operates. Maybe there needs to be more officers or fewer inmates out of their cells at that particular unit.
“I really hope Tasmania understands what a difficult job this is and why these people need to be admired for being able to go back to a workplace and face these situations. And then there is the families of these people, who are very worried about their loved ones going back to work.”
Guards at the prison do not carry weapons, he said.
“Some of them carry some sort of equipment, like capsicum spray, but they are vulnerable,” Mr Lynch said.