Today in Nice: Two arrested day after ISIS claims truck attack in France

Nice, France (CNN)French authorities arrested a man and a woman Sunday in the terror attack that killed 84 people in Nice last week, a prosecutor said.

Mohamed Lahouaiej Bouhlel, 31, drove a 20-ton truck through hundreds gathered to watch the Bastille Day fireworks on the Mediterranean city's waterfront Thursday.

Agnes Thibault Lecuivre, a spokeswoman for the anti-terrorism prosecutor, confirmed the arrests, but did not provide details on their connection to the terror attack.

French authorities earlier said they had been questioning five people Saturday. Among them was Bouhlel's ex-wife, who was taken into custody Friday, the anti-terrorism prosecutor's office said. The other four were men.

Bouhlel was shot to death by police after he barreled down the crowded Promenade des Anglais for almost a mile Friday, crushing and hitting people who had gathered to watch fireworks. More than 200 people were injured.

He was identified by fingerprints after his identification card was found in the truck, authorities said.

ISIS: 'Soldier' behind attack

ISIS' media group, Amaq Agency, said an ISIS "soldier" carried out the attack.

In a statement Saturday, it said "the person ... carried out the operation in response to calls to target nationals of the coalition which is fighting the Islamic State."

Bouhlel became rapidly radicalized and hadn't shown up on any anti-terrorist intelligence radar, said French Interior Minister Bernard Cazeneuve.

He had had no record of making militant statements and was not known to the intelligence services, the minister said.

"It seems he became radicalized very quickly," Cazeneuve said Saturday, without offering specifics.

Criminal record

Bouhlel, a resident of Nice, was born in Tunisia but had a permit to live and work in France.

He was identified by fingerprints after his identification card was found in the truck, authorities said.

He was known to police because of allegations of threats, violence and thefts over the past six years, and he was given a suspended six-month prison sentence this year after being convicted of violence with a weapon, authorities said.

Despite his criminal record, he was not on the radar for any kind of terror threat. The man was "entirely unknown by the intelligence services, whether nationally or locally," French prosecutor Francois Molins said.

"He had never been the subject of any kind of file or indication of radicalization."

Threat to France

Bouhlel's father, who lives in Tunisia, said his son showed signs of mental health issues -- having had multiple nervous breakdowns and volatile behavior, said CNN terrorism analyst Paul Cruickshank.

Cruickshank said "no country in the Western world is threatened more by jihadis and terrorism than France."

"This is a big step back here. They are absolutely exhausted after a year and a half of intense efforts to try and protect this country," Cruickshank said.

"The painful reality here is that if it wasn't going to be this promenade, it would have been any other promenade."

France had put intense security in place for Euro 2016, the international soccer tournament that just ended. No major attacks occurred during the event.

29 still in intensive care

About 85 people are still hospitalized in the wake of the attack, with 29 patients in intensive care, said Marisol Touraine, French minister of social affairs and health.

Touraine said of those in intensive care, 18 patients remain "between life and death," including one child.

Around 500 people in Nice have sought psychological support in the aftermath of the attack, she added.

Margot Haddad reported from Nice and Susannah Cullinane wrote in Auckland. CNN's Peter Wilkinson, Jason Hanna and Euan McKirdy contributed to this report