The attack late Saturday came as France is at its highest alert level against the background of the war between Israel and Palestinian militant group Hamas and following a series of isolated attacks in the country.

The incident has increased security concerns in the runup to the Paris Olympic Games this summer.

The case is being handled by French anti-terrorist prosecutors who have opened an investigation into a “terrorist” plot.

Armand Rajabpour-Miyandoab, a French national born in 1997 to Iranian parents, is a known extremist who has sworn allegiance to ISIS and was under psychological surveillance for mental health issues.

He was arrested over killing a 23-year-old man, identified as a German-Filipino citizen, with two blows from a hammer and four from a knife, as well as wounding two others.

Rajabpour-Miyandoab will in the afternoon appear before the investigating magistrate who is then expected to formally charge him ahead of trial, the source said.

He told investigators he acted “in reaction to the persecution of Muslims around the world,” a source close to the investigation said, describing him as “very cold" during questioning.

He said he picked the Eiffel Tower as “he could not bear it being lit up in the colors of the Israeli flag,” the source said, after attacks by Hamas in Israel on October 7 that killed 1,200 people, mostly civilians, according to Israeli authorities, and saw some 240 hostages taken.

Israeli bombardment has since killed more than 16,000 people in Gaza, most of them women and children, the Hamas-run government there says.

Rajabpour-Miyandoab, whose family is not religious, converted to Islam at 18 and began consuming huge amounts of ISIS propaganda, according to prosecutors.

He had previously been sentenced to five years in prison in 2016 for planning an attack, before he was released in 2020.

France’s Interior Minister Gerald Darmanin said on Monday that there had been a “psychiatric failure” in his case, as “doctors said on several occasions that he was doing better.”

His mother had reported concerns about him as recently as October, but that there was insufficient proof at the time to take legal action.