A massive manhunt was underway in France on Wednesday for an armed gang that killed two prison officers and seriously injured three others to spring an inmate they were escorting.

French Interior Minister Gerald Darmanin said “unprecedented” efforts were deployed, with hundreds of officers mobilised in the search for the escaped convict, Mohamed Amra, and the assailants who ambushed the convoy transporting him on Tuesday.

The violence of the attack shocked France. Prison workers held moments of silence Wednesday outside prisons in Paris and elsewhere to commemorate the officers who were killed.

Darmanin, speaking Wednesday on RTL radio, expressed hope that Amra could be caught “in the coming days.” Without giving full details about the extent of the manhunt, he said 450 officers had been deployed in the region of the attack to search for the assailants and clues about their whereabouts.

“The means employed are considerable," he said. “We are progressing a lot.”

The convoy was transporting Amra back to jail in the Normandy town of Évreux after a court hearing in Rouen when it was ambushed on the A154 freeway.

Amra, 30, had a long criminal record, with at least 13 convictions for robbery and other crimes, the first when he was just 15, said Paris prosecutor Laure Beccuau.

One of the officers killed was a 52-year-old captain in the prison service, where he had worked for nearly 30 years, and a father of two, the prosecutor said. The other officer killed, aged 34, was a married father-to-be, she said.