The suspected assailant had been arrested a month ago for carrying a screwdriver, but was not on police radar for Islamic radicalisation, France’s interior minister Gerald Darmanin said.
He said the screwdriver was considered a weapon, but did not explain why.
Two people were wounded in Friday’s attack, and two suspects were arrested, although the links between the pair were not immediately clear.
The two casualties’ conditions are not said to be life-threatening.
The main suspect was arrested on the steps of the Bastille Opera in eastern Paris, authorities said.
The site is not far from where Friday’s attack took place, outside the building where the weekly Charlie Hebdo was located before the 2015 attack.
The interior minister said the assailant arrived in France three years ago as an unaccompanied minor, apparently from Pakistan, but his identity is still being verified.
“Manifestly it’s an act of Islamist terrorism,” Mr Darmanin said in an interview with public broadcaster France-2.
“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 in Paris.
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 cigarette break.
An investigation was opened into “attempted murder in relation to a terrorist enterprise”, according to prosecutors.
French prime minister Jean Castex said the lives of the two wounded workers lives are 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”.
Mr Castex promised the government’s “unfailing attachment to freedom of the press, and its determination to fight terrorism”.
People in the area were stunned, saying on French TV that they were reliving the nightmare of the newsroom massacre.
In a tweet, Charlie Hebdo strongly condemned the stabbings.
— Charlie Hebdo (@Charlie_Hebdo_) September 25, 2020
The newspaper said: “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 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.
His colleague, Luc Hermann, describing witnesses’ version of the attack, said the assailant first struck the woman in her face, and then the man, before returning to attack the woman again.
He told France-2: “The whole team … took refuge on the roof of the building like our team did five years ago during the attack of Charlie Hebdo.”
Mr Hermann said it was “incomprehensible” that authorities had not taken special security precautions particularly at this time.
The Charlie Hebdo attacks trial is currently unfolding at the main Paris courthouse. Fourteen people, including three fugitives, are accused of helping the attackers in the January 2015 killings.
The interior minister conceded that security was lacking on the street where Charlie Hebdo was once headquartered. He said that 775 police protect its new location.
But “there was an attack, so we could have done better”, he said.
The minister said he has ordered special protection for all “symbolic sites”, noting in particular Jewish sites ahead of the Yom Kippur holiday this weekend.
A Jewish grocery was targeted days after the Charlie Hebdo newsroom massacre in what authorities say were coordinated attacks.
Charlie Hebdo has recently reproduced caricatures of the Muslim prophet that stoked the ire of some Muslims when first produced.
