The department of correctional services says it is appalled by the stabbing of three officials at St Albans prison in the Eastern Cape by inmates on Thursday.
"The incident took place around 11.30am as officials were busy with lock-up following the mandatory daily exercise," said the department's spokesperson Singabakho Nxumalo.
Nxumalo said the prison guards were in a stable condition, getting the best possible care, and an internal investigation had been launched.
"Although the inmates involved have been identified, an internal investigation has been established which will shed more light on this unfortunate incident," he said.
The attack has been reported to the police for a criminal case to be pursued.
Nxumalo described the incident as a clear act of hooliganism which would never be tolerated by the department.
"Correctional services will leave no stone unturned in making sure that all those involved are brought to book and that the law takes its course," he added.
The department said it would continue to monitor the behaviour of inmates and root out any elements that may threaten safety in prison facilities.
