According to him, he entered Italy through the island of Lampedusa on September 20, and arrived in Paris on October 9.
On October 29, three people were killed in an attack on parishioners in a church in central Nice.
According to the mayor of the city, Christian Estrosi, the crime was committed by a "radicalized Muslim".
French President Emmanuel Macron called the incident a terrorist attack.
As Prime Minister Jean Casteks said, the government's response "will be firm, ruthless and immediate."