PARIS — DNA traces on an orange juice bottle and a surveillance video of a man praying in a mall led to the arrest Wednesday of a young suspected Islamist extremist accused of stabbing a French soldier patrolling a crowded area just outside Paris, officials said.
The attack came days after a British soldier was slain on a London street in broad daylight, raising fears of potential copycat attacks.
The case also brought into question what authorities knew about the suspect, identified by police as Alexandre Dhaussy, because he had been tracked over several years.
France has been on heightened security alert since its military intervention in January in the west African nation of Mali to oust Islamist radicals.
The French soldier attacked on Saturday is recovering from his injuries and has been released from the hospital.
The suspect was captured on camera offering a Muslim prayer in a corner of a busy shopping mall 10 minutes before he went after the soldier Saturday at the La Defense financial and shopping district, French prosecutor Francois Molins said Wednesday at a news conference in Paris.
The 22-year-old Frenchman bought the juice and the pocketknife used in the attack an hour beforehand, Molins said.
‘‘The intent to kill is obvious. The suspect doesn’t hesitate to stab several times with impressive determination,’’ Molins said.
The suspect was arrested Wednesday morning outside Paris at the house of a friend who has not been implicated.
‘‘The suspect implicitly confessed when he told police ‘I know why you’re here,’ ’’ Molins told reporters. ‘‘The nature of the attack, the fact that it happened three days after the London attack, and a prayer that was [said] shortly before the attack, make us believe that he acted in the name of his religious ideology and that his wish was to attack someone representing the state.”
Dhaussy, who was unemployed and homeless, was identified through DNA on a plastic juice bottle, said Christophe Crepin, spokesman for the police union UNSA.
The prosecutor said the suspect had converted to Islam around age 18. Authorities had his DNA profile on record after a series of petty crimes as a minor.
Intelligence officials operating in Yvelines, west of Paris, had tracked Dhaussy over several years. However, information gleaned on him, like his refusal in 2011 to take a job placing him in contact with women, never got bumped up to a national level, a statement by the French National Police headquarters said.
The statement said the acts, including his praying in the street in 2009, were ‘‘characteristic of fundamentalist behavior’’ that did not justify sending the information to the DCRI, as the national intelligence agency is known.
While looking for a job with a publicly financed agency, Dhaussy did say he wanted to follow religious training abroad, the statement said.