While no details on the pair have been released, French anti-terrorist investigators have expressed increased concern over the young age of some suspects detained in recent months for planning militant attacks.

The 19-year-old has been charged with “terrorist conspiracy” to commit attacks and the “acquisition and possession of arms for a terrorist enterprise,” said the judicial source, speaking on condition of anonymity.

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The youth aged under 18 was detained on June 13, the source said.

The pair made contact on social media and were planning a “a violent action notably aiming at Jewish targets,” said the source without giving details on the plot.

Anti-terrorism investigators say a growing number of youths have been held in recent months for preparing attacks.

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“This is a necessarily worrying phenomenon,” senior anti-terrorist prosecutor Olivier Christen said at an evidentiary hearing on Wednesday.

French politicians have also condemned a growing number of attacks on the country’s Jewish community, the biggest outside Israel and the United States.

Outrage has been expressed over the rape of a 12-year-old Jewish girl in a park in the Paris suburbs last Saturday. Two 13-year-old boys have been charged with rape and making anti-Semitic insults.

Several protest rallies have been held in Paris and other French cities over the case which comes as France prepares for a national election in which the far-right National Rally party is tipped to make major gains.