Inmate Michaël Chiolo wounds guards at France's Condé-sur-Sarthe prison

A prison inmate in northern France has seriously wounded two guards in a knife attack, in what French ministers have described as a "terrorist incident".

Michaël Chiolo was later detained in a police operation carried out on Tuesday evening.

He and his female partner, who was visiting him, had been barricaded in the family-visiting area of a Normandy high-security prison since the morning.

Both were shot by police, and she is now said to have died of her wounds.

One of the guards suffered a serious abdominal wound, while the second was slashed on the face and back, reports say.

Chiolo shouted "Allahu Akhbar" (God is Greatest) during his attack, reports said.

"It was truly a murder attempt. There was blood everywhere. The family-visiting unit was a battle scene," a prison staff representative told AFP news agency.

It is thought the ceramic knife Chiolo used might have been smuggled into the prison by his partner, Justice Minister Nicole Belloubet said.

Chiolo, who was serving a 30-year sentence, reportedly became radicalised while in prison.

He said he wanted to avenge the death of Cherif Chekatt, who carried out the Strasbourg shooting attack in December, Paris prosecutor Rémy Heitz said on Tuesday night.

The two men had previously spent 175 days in jail together, and then continued to correspond by mail, franceinfo reports on its website.

Chiolo had been jailed for choking an 89-year-old man, whom he and an accomplice had tied up while burgling, to death.

While in jail, he was sentenced to an extra year in prison for condoning terrorism. He had asked fellow inmates to "re-enact" the 2015 terror attack on the Bataclan music venue in Paris, which left 90 people dead.