French anti-terror prosecutors are investigating a knife attack by a prison inmate that injured two guards in western France.

Justice Minister Nicole Belloubet said the prisoner's wife was visiting him Tuesday and he locked himself in a visiting room after stabbing the guards with a ceramic knife. She says the guards' injuries are not life-threatening and no hostages were taken.

Belloubet says "there's no doubt about the terrorist nature of the attack" at the Conde-sur-Sarthe prison.

The Justice Ministry said the inmate had convictions for kidnapping leading to death, armed robbery and glorifying terrorism.

Local media say the inmate was known as a radicalized Islamist. They say he was sentenced in 2015 to a 30-year prison term for the murder of an 89-year-old man who had survived Nazi concentration camps.