French police blockades the crime scene in Nice, France, October 29, 2020. (Photo: AFP/VNA)

Authorities are interrogating six people to find out if they are linked to 21-year-old Tunisian Brahim Aouissaoui, who prosecutors say carried out the knife rampage early Thursday morning at the Notre-Dame Basilica.

Aouissaoui, who is reported to have beheaded a woman and killed two other people, arrived in France in early October.

French authorities have raised the national security alert to its highest level and doubled anti-terrorism forces to seven thousand men.

French Foreign Minister Jean-Yves Le Drian said France is facing a security threat from everywhere.