Five people aged 15-17 have been taken into custody in eastern France over the defacement of hundreds of Jewish graves.
The youngest came forward after seeing the outrage over the attack, in which more than 300 tombstones in the town of Sarre-Union were desecrated.
France's interior Minister, Bernard Cazeneuve, called the vandalism "a despicable act". He added: "The country will not tolerate this new injury which goes against the values that all French people share."
It is not the first time that the Jewish cemetery in the town has been targeted. In 2001, 54 graves were vandalised.
Also last weekend, French police arrested a Muslim teenager for emailing death threats to two Jewish leaders.
The 19-year-old, reportedly known only as "Amin", sent videos of the beheadings of Islamic State hostages to Israel's consul-general in Marseille, Barnea Hasid, and a French Jewish MP, Meir Habib. He threatened the Jewish officials with "a similar fate".
After a three-day interrogation by police, he was put under house arrest until the start of his trial on April 2.
His family said he was confused and had been reading about Islamic Jihad.
Meanwhile, in Paris, Israeli journalist Zvika Klein documented 10 hours of antisemitic abuse, hurled at him as he walked around the city wearing a kippah. A video, recorded by a colleague, shows bystanders hurling insults and threats in his direction. Mr Klein, a reporter for the news website nrg.co.il, said he wanted to test attitudes to Jews.
Mr Klein told JTA that when he was walking through the suburb of Sarcelles, home to a large Muslim population, he received more abuse than wandering through the centre of the city. The video, filmed by the colleague wearing a backpack fitted with a rear-pointing camera, shows Mr Klein being subjected to racist and homophobic abuse.