Five adolescents aged 15 to 17 have been taken into custody in eastern France for questioning over a massive vandalism attack against Jewish graves, a local prosecutor said on Monday.
All five are from the region of Sarre-Union in Alsace, where around 300 tombs were defaced over the weekend.
The youngest came forward after being shocked by the massive reaction across the country to the vandalism, prosecutor Philippe Vannier said.
"Apparently, he was very very affected by the scale of the reaction to this affair, including the statements from the highest state authorities," Vannier told reporters.
The boy, who was encouraged to hand himself in by one of his friends, has denied any anti-Semitic motive, Vannier added.
"We don't know the motives of these adolescents who don't have past criminal records and we don't know of any ideological convictions that could explain their behavior.
"They are very very shocked by the turn of events."
The five boys pushed over tombstones in the cemetery and opened up vaults. A monument to the victims of the Holocaust at the entrance was also vandalised.
Following news of the attack, French Interior Minister Bernard Cazeneuve denounced it as "a despicable act".
"The country will not tolerate this new injury which goes against the values that all French people share," he said, vowing that "every effort will be made to identify, question and bring to justice the person or persons responsible for this ignominious act."
French Prime Minister Manuel Valls, writing on Twitter, also condemned the desecration, calling it "an anti-Semitic and ignoble act".
It is not the first time that a Jewish cemetery in Sarre-Union has been targeted.
In 1988, around 60 Jewish steles, stone or wooden slabs often used for commemorative purposes, were knocked over while in 2001, 54 tombs were wrecked.
It comes as France's more than half a million-strong Jewish community is feeling increasingly vulnerable after last month's deadly attacks in Paris, and amid a steady rise in already high levels of anti-Semitism.
Record numbers of French Jews are already emigrating - particularly to Israel - due to anti-Semitism compounded by a weak economy, but the murder of four Jewish shoppers in a Paris supermarket in January has caused even more to consider to move.
Earlier Monday, Prime Minister Valls called on French Jews not to flee the country, pledging his government's commitment to fighting anti-Semitism.
"My message to French Jews is the following: France is wounded with you and France does not want you to leave," Valls said.
AFP contributed to this report.