French officials say a man who is suspected of stabbing two people Friday in Paris has said he was targeting what he thought were the offices of the satirical magazine "Charlie Hebdo" because it had recently republished cartoons featuring the Prophet Muhammad.

The attacker was identified as an 18-year-old Pakistani man who arrived in France three years ago as an unaccompanied minor. 

He was apparently unaware that the magazine had moved from that location, following a 2015 attack that killed 17 people.

French authorities launched an anti-terrorism investigation after the attack on Friday.

In an interview with France 2 television station, French Interior Minister Gerald Darmanin said the attack was "clearly an act of Islamist terrorism." 

On Sunday, Darmanin visited a synagogue and said more than 7,000 police and soldiers are protecting Jewish services as the Jewish holy day of Yom Kippur, the Day of Atonement, begins.

"Because we know that Jews are particularly targeted by Islamist attacks," Darmanin told reporters, "we should obviously protect them."

Jean-Francois Ricard, France's counterterrorism prosecutor, said the attacker did not know the victims - a woman and a man from a documentary production company on a smoke break.  

French police said on Saturday they had detained a person believed to be a former roommate of the man who attacked the people.

Late Friday police released a 33-year-old Algerian man who was a witness and had "chased the assailant," after the investigators corroborated the man's account.

A terrorism trial for 14 people accused of being accomplices in the 2015 attack on the magazine is currently going on in Paris.   

"Charlie Hebdo" angered many Muslims by publishing cartoons featuring the Prophet Muhammad, and ahead of the trial it recently reprinted some of the same cartoons.     

Police recently moved the magazine's head of human resources from her home after she was the target of death threats around the start of the trial.