The world is facing another terror attack in Paris, which has killed more than 130 people and injured more than 350.
French President Emmanuel Macron has vowed to “fight against terrorism” and has called for “a full investigation” into the incident.
France’s top prosecutor has also been investigating the attack.
In a statement on Sunday, the prosecutor general’s office said it had opened an inquiry into “whether or not the attacker acted alone”.
It said it would be looking into the role of “terrorist groups” and “whether any links were established with jihadist networks.”
France has been hit by several terrorist attacks in recent years, including a string of bombings in January, which left 130 people dead and around 230 injured.
France has also seen the biggest-ever influx of refugees to Europe, with some 800,000 people crossing the Mediterranean to reach the continent.
More than half of them have been killed, according to UN figures.
France will hold a minute’s silence for the victims of the attack on Monday, marking the one-year anniversary of the attacks.
France is now the second country after the UK to ban the wearing of face veils in public, after a French court ruled that it was unconstitutional.
The French authorities have been criticised for their handling of the case, including by some of the victims’ relatives.
In November 2016, a judge ruled that the veil should be banned in public places.
The head of the French parliament’s justice committee, Bernard Lapierre, said the veil is an “essential symbol” and should be abolished.
“It is not a veil, it is a mask,” he said.
“We have the right to choose our own symbols.”
He also said the law should be amended to cover “veil-less” clothing.
