In his first comments on the murder of a 12-year-old girl, Emmanuel Macron described it as an act of “extreme evil.”
The French president stated that the family of the girl, Lola, deserved “the nation’s esteem and care.”
Lola’s body was discovered in a plastic trunk outside her apartment building in Paris last Friday.
A 24-year-old woman has been remanded in custody on suspicion of murder, rape, and acts of torture.
The woman is an Algerian immigrant whose residence permit had expired and who was under orders to leave the country.
Parties on the right and far-right have focused on this as a sign of a weak immigration policy.
Members of the far right held a rally in memory of Lola on Thursday in Paris, despite pleas by her family not to politicise her death.
In Brussels, where he was attending a European Council summit, Mr Macron told journalists: “I think all parents experience in their flesh what Lola’s parents experience.
“I think of her parents, her brother, and her half-brother, the distress of this family which is incredibly dignified and united.
“When we are faced with extreme evil, and we experience that it is possible in our society and that it is there, that is what is dizzying,” he added.
A tribute is being organized in the northern town of Fouquereuil, where Lola’s family is from and where they have retreated.
She is due to be buried on Monday in another local northern town. Interior Minister Gérald Darmanin is due to attend, invited by her parents, according to BFMTV.
Lola disappeared last Friday after failing to make the short walk home from school in the 19th district of northeast Paris. By late evening, her body had been found inside a trunk on wheels.