ISIS Claims Responsibility for Attack on Nice, 5 Detained by French Officials

— -- ISIS has claimed responsibility for Thursday's deadly truck attack in Nice, France, according to a statement released this morning by the group's media outlet.

Mohamed Lahouaiej Bouhlel, a 31-year-old Tunisian citizen and resident of Nice who worked as a delivery man, drove a truck into a crowd during Bastille Day celebrations, killing at least 84 people and injuring 202 others. Four children remain in critical condition. One of whom is 10-years-old, but his identity remains unknown, since authorities are still trying to find family members.

The Aamaq news agency on Saturday cited a "security source" as saying the attacker -- it did not name Bouhlel -- "carried out the operation in response to calls to target the citizens of coalition countries fighting the Islamic State." The group also described the attacker as a "soldier" of the organization.

The terror group's claim comes as French president Francois Hollande chairs a security and defence meeting in Paris at 9 a.m. local time.

Five individuals have also been detained for questioning by French authorities, following Thursday's attack, a spokeswoman for the French prosecutor's office said Saturday.

One of the five people detained by police is Bouhlel's ex-wife, who was taken into custody Friday morning. The four others are not family members, but friends or acquaintances.

Investigators are working to determine whether Bouhlel had any accomplices.

A vigil for the victims was slated for this morning, but it was cancelled by officials who cited security reasons.

The promenade and beaches are due to reopen at noon local time on Satuday.

During an interview with French radio, Bouhlel's father said he had not seen his son in four years. He also claimed he had psychiatric problems.

This story is developing. Please check back for updates.

ABC News' Louise Dewast contributed to this report.