Two suspects were arrested separately shortly after the stabbing in which two people were wounded.
The main suspect had been arrested a month ago on the steps of the Bastille Opera, not far from the attack site, for carrying a screwdriver but was not on the police radar for Islamic radicalisation.
The interior minister said the young man arrived in France three years ago as an unaccompanied minor, apparently from Pakistan, but his identity was still being verified.
“But manifestly it’s an act of Islamist terrorism,” Interior Minister Gerald Darmanin said in an interview with the France 2 television station. “Obviously, there is little doubt. It’s a new bloody attack against our country, against journalists, against this society.”
France’s counter-terrorism prosecutor said earlier that authorities suspect a terrorist motive because of the place and timing of the stabbings: in front of the building where Charlie Hebdo was based until the Islamic extremist attack on its cartoonists and at a time when suspects in the 2015 attack are on trial.
Prosecutor Jean-Francois Ricard said that the chief suspect in Friday’s stabbings was arrested, along with another person.
Mr Ricard said the assailant did not know the people who were stabbed, a woman and a man working at a documentary production company who had stepped outside for a smoking break.
The suspects’ identities have not been released. An investigation was opened into “attempted murder in relation with a terrorist enterprise”, according to an official at the terrorism prosecutor’s office.
French Prime Minister Jean Castex said the lives of the two wounded workers were not in danger. He offered the government’s solidarity with their families and colleagues.
The prime minister noted the “symbolic site” of the attack, “at the very moment where the trial into the atrocious acts against Charlie Hebdo is under way.”
He promised the government’s “unfailing attachment to freedom of the press, and its determination to fight terrorism”.
In a tweet, Charlie Hebdo strongly condemned the stabbings.
“This tragic episode shows us once again that fanaticism, intolerance, the origins of which will be revealed by the investigation, are still present in French society….There is no question of ceding anything,” the newspaper said.
The two people confirmed injured worked for documentary film company Premieres Lignes, according to founder Paul Moreira. He told France’s BFM television that the attacker fled into the subway, and the company’s staff members were evacuated.
Mr Moreira said a man in the street “attacked two people who were in front of the building, didn’t enter the building, and who attacked them with an axe and who left”. He said the company had not received any threats.
A tweet from Charlie Hebdo posted not long after the attack said: “All the team at Charlie offers support and solidarity to its former neighbours and colleagues at PLTVfilms and to the people hit by this odious attack.”