Two inmates used “improvised bladed weapons” in the assault at Whitemoor jail, a maximum-security facility 120 kilometres north of London.
An attack on a prison officer in the UK is being treated as terrorism, police say.
Two inmates used “improvised bladed weapons” in the assault at Whitemoor jail, a maximum-security facility 120 kilometres north of London.
One officer was seriously injured while another four staff members were hospitalised in the attack on Thursday morning.
Police confirmed on Friday afternoon that the case was now being treated as a terrorist incident.
"The incident itself was quickly contained and dealt with by prison staff and from our enquiries thus far, there is nothing to suggest any continuing threat inside or outside of the prison system linked to yesterday's incident," the Metropolitan Police said in a statement.
"Both the prisoners suspected to have been involved in the attack remain in prison. No arrests have been made at this time."
Steve Gillan, general secretary of the Prison Officers Association, called it a “cowardly and vicious attack” on “hard-working staff.”
“There is no doubt in my mind that, but for the bravery of staff, this morning we could have been talking about the death of a prison officer,” he said.
In March 2019, a prison inmate in France seriously injured two guards in what was also treated as a "terrorist attack."