LONDON (AP) — Two inmates wearing fake suicide belts attacked and wounded a guard at a maximum-security prison in England, police said Friday. Detectives are treating the incident as a terrorist attack.

The Metropolitan Police force said the officer was injured in the head and neck with “improvised bladed weapons” during the Thursday attack at Whitemoor prison in eastern England. Four other prison staff members who came to the guard's assistance were also hurt, the police force said.

All five were treated at a hospital and released.

Police said the attackers were “wearing belts with various items crudely attached.” The two inmates were subdued and detained by prison staff.

Deputy Assistant Commissioner Dean Haydon, the force's counterterrorism coordinator, said the violence was being treated as a terrorist attack, “and the investigation continues at pace.”

U.K. media have identified one of the attackers as 24-year-old Brusthom Ziamani, who was jailed in 2015 for plotting to behead a British soldier.