The entrances to 18 prisons in France were blocked by guards Wednesday who burned tires and other materials at the gates in protest of the stabbing of two colleagues at a jail in the northwest of the country in what has been described as a "terrorist" attack.

Outrage was ignited on Tuesday when Michael Chiolo, a "radicalized" inmate at the Condé-sur-Sarthe jail, seriously wounded two guards when he stabbed them with a ceramic knife. The inmate was visiting with his wife when the attack occurred, and authorities believe she may have snuck the knife into the facility with her. The inmate and his wife were both shot in the ensuing confrontation, leaving his wife dead.

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Justice Minister Nicole Belloubet condemned the attack at Condé-sur-Sarthe on Tuesday, saying it was "no doubt" in a "terrorist nature." Chiolo reportedly shouted "Allahu Akhbar" during the stabbing, according to The Local.

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Condé-sur-Sarthe is reportedly one of the nation's most secure jails, and is not plagued by overcrowding like some other facilities in the country, Belloubet added. It is home to a specialized wing which was created for radicalized inmates in September. Chiolo, however, was not being housed there before Tuesday's attack.

Guards say that attacks by inmates are becoming more common, and demand action. The protests on Wednesday saw blockades at least 18 prisons across the country, as guards prohibited staff or visitors from entering the facilities.

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"Colleagues want to go to work but we do not abandon them, we do not send them to die," a union leader said outside the Fleury-Merogis prison outside Paris said,

Last year, protests were held for three weeks by prison staff at a high-security jail in northern France after a guard was attacked by a jihadist inmate.