He made the statement on Sunday (11 Sept.) in light of the event the previous week when French officials said they foiled the plans of a terrorist cell guided by the Islamic State to attack a railway station in Paris.
The 15-year-old, already on a high-security threat list, was arrested on Saturday, one week after French police prevented an attack in central Paris by a group of female Islamic State followers who tried to blow up a vehicle filled with gas bottles.
The three were brought before anti-terrorism judges. 29-year-old Ornella G. was not the shot woman, but was in connection with that attack, and was immediately put under investigation when her fingerprints were connected with the vehicle outside Notre Dame cathedral last week.
The 19-year old woman, Ines Madani, had a letter in her purse where she swore alliance and obedience to the Islamic State.
The youth had written to contacts on Telegram - the encrypted messaging app widely used by jihadists in France - of his plans to carry out a knife attack, sources said.
Paris - French Prime Minister Manuel Valls has said: "Today the threat is at a maximum, and we are a target". Officers found a vehicle filled with gas cylinders near Notre Dame cathedral, which they believe female militants directed by Islamic State planned to detonate at a Paris railway station. The two younger women were known to police for their links to Islamist radicals.
Upon checking the vehicle, the police found the gas canister, a partially smoked cigarette, and lid covered with gasoline.
One of the women was charged with terrorism offences after telling police she and an accomplice had tried to set the vehicle alight but fled when they saw a man they believed to be a plain-clothes policeman.
The unnamed youth was arrested at his home near the Coulée Verte, a "green corridor" walkway in Paris similar to New York's High Line, where detectives allege he was planning to stab random passers-by last weekend. Those arrested included a 15-year-old girl, the daughter of one of three women arrested south of Paris.
France is in a state of emergency after three attacks this year, including the Bastille Day truck attack in Nice that killed 86 people. 196 jihadists have died in Iraq or Syria.
This image from video provided by the SITE Intelligence Group shows Rachid Kassim as he appeared on a video released on militant websites on July 20, 2016.
He also exchanged messages with the murderers of priest Jacques Hamel.