Two people were on Friday severely injured in a knife attack in Paris near the former office of the satirical magazine Charlie Hebdo in what officials have branded an "Islamist terror attack".
Two people had been arrested by 15:00 CET, Jean-François Ricard, national anti-terrorism prosecutor, confirmed.
Ricard said police had detained the person who they believed was behind the attack and that a second individual was taken in to determine his links to the alleged attacker.
"Given the location of the attack, in front of the building where the Charlie Hebdo newsroom used to be, the time of the facts, during the trial, and finally given the materialisation of the facts, there was a clear desire by the perpetrator to kill two people," he added.
An investigation for "attempted assassination in connection with a terrorist enterprise" and "criminal terrorist association" has been opened.
Five other people were also detained later in the day in connection to the incident, police sources told AFP.
French Prime Minister Jean Castex said that the two victims' lives were not in danger.
Link to Charlie Hebdo?
The two victims work for production company Premières Lignes, whose offices are located in the same building as the former Charlie Hebdo offices.
The offices were the scene of an attack in January 2015 that saw 12 people killed, including many of the magazine's staff. Fourteen people are currently on trial over the 2015 attack.
Paul Moreira, a journalist at the production agency, told BFM-TV that his wounded colleagues were young employees who were outside the building. He said the company had not previously received threats.
Police said earlier in the afternoon that a cordon had been put up near the building due to a suspect package. A large butcher's knife was reportedly found near the metro station in the area.
The motive is so far unclear and it is uncertain whether the attack is linked to the 2015 killings.
The Académie de Paris told Euronews that schools in the 3rd, 4th and 11th districts of Paris have been temporarily locked down, with children staying inside. Parents were invited to come and collect their children at 15:00 CEST, "the precautionary measures having been lifted," police said.
The city of Paris said that care homes have also been locked down in the area.
France 'at war' against Islamist terrorists
Castex, who visited the scene in the early afternoon alongside Paris Mayor Anne Hidalgo and Interior Minister Gérald Darmanin, said he "wanted to show my solidarity with the families of the victims and also to all the colleagues of these two journalists".
"I reaffirm our unwavering attachment to freedom of the press, the fight against anti-terrorism and I wish to affirm our full mobilisation to the nation," he added.
Darmanin later told France 2 that the country is "still at war with Islamist terrorists. We are still at war with them."
"It is in the process of mutating because the work that our armies are doing to destroy the Islamic State, diminishes, but does not completely prevent what we call projected attacks, those orgaised from abroad.
"Obviously isolated people are committing terrorist acts in the name of radical Islam and we must fight them," he added, stressing that intelligence services had foiled 32 terror attacks in three years.
'Terror doesn't have a place in Europe'
"Charlie's entire team provides its support and solidarity to its former neighbours and colleagues at Premieres Lignes and to those affected by this heinous attack," Charlie Hebdo tweeted.
"This tragic episode demonstrates once again that fanaticism and intolerance, the origins of which the investigation will reveal to us, are still present in French society. Far from terrorising us, such events should make us even more combative in the defence of our values," it added in a statement.
Politicians have also reacted with shock and sadness over the news of the attack.
European Council President Charles Michel tweeted that his thoughts went to victims, adding: "terror doesn't have a place on the European territory."
President of the region Valérie Pécresse said she was "extremely shocked by the deadly attack near the former premises of #CharlieHebdo, in a district of Paris which has already paid a heavy price for terrorist violence."
Italian Prime Minister Guiseppe Conte expressed his "solidarity with France in the face of the vile attack around the former premises of Charlie Hebdo".
"Italy stands by those who fight violence in all its forms," he added.
Watch video images from the scene in the player above.