The chief suspect in a double stabbing in Paris told investigators he carried out the attack in anger over caricatures of the Prophet Muhammad recently republished by satirical weekly Charlie Hebdo, a judicial official has said.

Two people were wounded and seven are in custody after Friday’s attack with a meat cleaver outside the newspaper’s former offices in eastern Paris, which counter-terrorism authorities are investigating as an Islamic extremist attack.

Charlie Hebdo lost 12 employees in an al Qaida attack in 2015 by French-born extremists who had criticised the prophet cartoons.

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Police at the scene (Thibault Camus/AP)

The newspaper, which routinely mocks religious figures of all kinds, decided to republish the caricatures the day before the trial into the 2015 attacks opened earlier this month. The publication drew threats from militant groups as well as criticism from Muslims in multiple countries.

Questioned by investigators, the chief suspect acknowledged carrying out the attack and said he sought to target Charlie Hebdo because of the caricatures, according to an official close to the investigation.

The suspect had been arrested a month ago for carrying a screwdriver, but was not on police radar for Islamic radicalisation, interior minister Gerald Darmanin said. He said the screwdriver was considered a weapon, but did not explain why.

The suspect arrived in France three years ago as an unaccompanied minor, apparently from Pakistan, but his identity was still being verified, the minister said.

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A French police officer guards a nearby street (Lewis Joly/AP)

Seven others were detained in the aftermath of Friday’s attack, but one has been released, the official said. Five of those in custody were detained in the Paris suburb of Pantin in a residence where the suspect is believed to have lived.

The two people wounded in Friday’s attack were a woman and a man working at the Premieres Lignes documentary production company who had stepped outside for a smoke. Company co-founder Luc Hermann told broadcaster France-Info that they remained in hospital but their condition was “reassuring”.

Prime minister Jean Castex, visiting Paris police headquarters on Saturday, pledged to step up the fight against terrorism, saying: “The enemies of the republic will not win.”

The interior minister conceded that security was lacking on the street where Charlie Hebdo was once headquartered, and ordered special protection for all “symbolic sites”, noting in particular Jewish sites around the Yom Kippur holiday this weekend.

A Jewish grocery store was targeted days after the Charlie Hebdo newsroom massacre, in what authorities say were co-ordinated attacks.