Paris: A man who rammed a car into a police van in Paris stored a cache of weapons at his home and held a gun permit despite being on a secret service list of people linked to extremism, police sources and French officials said on Tuesday.
A judicial source said investigators were compiling an inventory of the arms and equipment found in the 31-year-old's home.
The man, who died in the attack, was also carrying in his car an assault rifle, two pistols, ammunition and two large gas canisters when he rammed a police convoy on Monday.
Prime Minister Edouard Philippe said the individual first received a permit to possess a gun before he was flagged to intelligence agencies as a potential militant threat.
At the time there was no reason to deny him the permit, Philippe said.
Philippe said it was "quite possible" the licence was active at the time the attacker was on a security watchlist.
Three sources close to the investigation confirmed it was.
"Nobody can be happy, and certainly not me, that someone who has been flagged to security agencies can continue to benefit from such an authorisation," Philippe told BFM TV.
The man was placed on France's so called 'Fiche S' watchlist after he was found to belong to a extremist movement, two police sources said. Individuals on the list are placed under surveillance though the intensity of that surveillance varies depending on the perceived threat the individual poses.
Philippe said draft legislation drawn up in May envisaged changes to allow officials who handle gun permits to check if individuals seeking licences are on a watchlist.
But refusing permits in such cases had it drawbacks, he said.
"If you revoke the authorisation of someone who is under surveillance, they're going to know why."
On Monday, witnesses saw the man being pulled from the car as thick yellow smoke poured out.
Police arrested four of his close relatives in a raid south of Paris late on Monday, a police source said.
They included his father and brother.
France has been on high alert after a wave of militant extremist attacks over the past two years, including most recently an attack on police outside the Notre Dame Cathedral and an IS-claimed attack on police on the Champs Elysees in April.
In July last year, 86 people were killed when a truck ploughed through a crowd in Nice, and similar incidents have occurred in other European cities.
Philippe said the government would be presenting a draft law soon to toughen counter-terrorism legislation.
"We need to find legal instruments that at once guarantee that we continue to live in a Fifth Republic which safeguards freedoms and ensure the security of French people," Philippe said.