PARIS -- A massive manhunt was underway in France on Wednesday for armed assailants who ambushed a prison convoy, killing two prison officers, seriously injuring three others and springing the inmate they were escorting. The prime minister vowed the gang would be caught, saying, “They will pay."

“We are tracking you, we will find you and we will punish you,” Prime Minister Gabriel Attal said in parliament, to applause from lawmakers. “They will pay for what they have done.”

The escaped convict, Mohamed Amra, 30, has a long criminal record, with at least 13 convictions for robbery and other crimes, the first when he was just 15, prosecutors said.

French Interior Minister Gerald Darmanin said “unprecedented” efforts were being deployed. Hundreds of officers were mobilized in the search for Amra and for the assailants who laid in wait for the prison van transporting him, ramming a car into it before opening fire 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 in Normandy in northern France to search for the assailants and clues about their whereabouts.

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

The attack appeared to have been carefully prepared. The convoy was transporting Amra back to jail in the Normandy town of Évreux after a hearing with an investigator in Rouen when it was ambushed on the A154 freeway.

The prison van and another prison escort vehicle had just gone through a toll booth on the freeway when the van was rammed head-on by a car. The Paris prosecutor's office said the car had been stolen and had gone through the toll booth a few minutes ahead of the prison convoy and then waited there.

Another car followed behind the convoy, seemingly boxing it in. Assailants sprang from the cars and opened fire, spraying the prison vehicles, Paris prosecutor Laure Beccuau said.

The assailants and Amra then fled. Two burned cars were subsequently found which investigators are examining, Beccuau said.

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, Beccuau said. The other officer killed, aged 34, was a married father-to-be, she said.