The assailant, who was killed by police following the attack at Place de l'Opera in central Paris on Saturday, is also thought to have been monitored by authorities for links to radical Islamists. A judicial source confirmed to AFP that the man was "French, born in Chechnya in 1997." His mother and father have been taken into custody for questioning, the source added.

Police also arrested a friend of the man in the eastern city of Strasbourg. He is currently being held for questioning.

The attacker has been identified by France 2 as Khamzat Azimov, a 20-year-old Russian-born immigrant who received French citizenship in 2010. According to AFP, Azimov had been on a list of people considered to pose a threat to national security, known as the 'Fiche S,' since 2016. France Info reports that he was also registered in the File for the Prevention of Terrorist Radicalization (FSPRT). He had no criminal record, judicial sources said.

According to Europe 1, Azimov was monitored for his connections in "radical Islamic circles."BFMTV reports that he had specific, indirect links with "a person in Syria."

The attacker reportedly shouted "Allahu akbar" during the attack in which five people were injured, two of them critically. One of the victims, a 29-year-old man, later succumbed to his injuries. Police found no documentation on the attacker, but investigators identified him by his fingerprints, Europe1 radio station reported on Sunday.

"At this stage, on the basis of testimonies mentioning the fact that the aggressor shouted 'Allahu akbar' when attacking passersby with a knife, given the modus operandi, we dispatched the anti-terrorist section of the prosecutor's office," Paris prosecutor Francois Molins said.

Islamic State (IS, formerly ISIS) claimed responsibility for the attack, the group's affiliated website Amaq said. However, investigators have not verified the organization's claim.