PARIS -- French investigations into a fatal weekend attack near the Eiffel Tower were looking Monday into the mental health of the suspected assailant, who swore allegiance to the Islamic State group before stabbing a German-Filipino tourist to death and injuring two other people with a hammer.

The French national taken into police custody, Armand Rajabpour-Miyandoab, has a history of mental illness and of Islamic radicalization, officials said. He faces a possible preliminary charge of terrorist-related murder for the Saturday night attack that raised fresh questions about security in Paris before it hosts the Olympic Games next year.

"This is a case that links radical Islam, undeniably, and mental illness. I must tell the French people the truth that there are numerous cases like this," French Interior Minister Gerald Darmanin said Monday, adding that around one-third of suspected radicals under surveillance have psychiatric issues.

The stabbing took place within the future security perimeter that will blanket both banks of the River Seine when the 2024 Summer Games open July 26 with a show and parade for the 10,500 athletes along the waterway that cuts through the French capital..

Expected to draw hundreds of thousands of spectators, the size and scope of the outdoor extravaganza make it a particularly daunting public safety challenge in a city that has been repeatedly hit by extremist attacks.

Sports Minister Amelie Oudea-Castera insisted Monday that France was capable of safeguarding the opening festivities. They will be the Olympics' first held outside of a stadium, which are easier to secure. There are no backup plans to move the event elsewhere, but the scale of the show and spectator numbers could be tweaked, if necessary, the minister said.

"We don't have a Plan B. There is a Plan A within which there are several sub-plans," Oudea-Castera said on France Inter radio.

The suspect in Saturday's attack previously spent more than 3 1/2 years in prison on a terror conviction. He was on a police list of feared radicals, was being watched by France's counter-terrorism surveillance agency and received mandatory psychiatric care until April of this year, officials said.

Speaking to broadcaster BFMTV, the interior minister said authorities should be given greater powers to force psychiatric treatment on people in such cases.

"There appears to have been a psychiatric failing because doctors on multiple occasions decided that he was better, that he was more normal and could live freely," Darmanin said.

A few weeks before the attack, the suspect's mother told police that her son had stopped taking his medication, but she was apparently too scared of him to ask that he be hospitalized, the minister said.

"She didn't want to, apparently because she was scared of her child, which is understandable," Darmanin said. "She came back a few days later to say that he seemed better."

The assailant apparently targeted victims at random. After fatally stabbing the 23-year-old tourist, the attacker crossed a bridge to the city's Right Bank and assaulted two people with a hammer. The British national and the French citizen were treated at a hospital before being released, authorities said.

In a video recorded before the attack, Rajabpour-Miyandoab swore allegiance to the Islamic State group and expressed support for Islamic extremists in Africa, Iraq, Syria, Egypt's Sinai, Yemen, Iran and Pakistan, according to France's anti-terrorism prosecutor, Jean-Francois Ricard.

The video, in Arabic, was published on Rajabpour-Miyandoa's account on X, formerly Twitter, where his recent posts included references to the Israel-Hamas war, the prosecutor said.