French authorities arrested four teenage girls on Tuesday on suspicion of communicating with jihadists in Syria via the encrypted messaging app Telegram, a judicial source told Reuters.
In a chatroom the suspects discussed the possibility of preparing violent attacks, the source said, without elaborating.
Three of the four girls are minors, aged between 15 and 17 years, and the fourth is 18 years old.
French TV channel France 3 reported that one of the girls was in contact with Rachid Kassim, a French Islamist militant who is suspected of having inspired some of the recent attacks in France.
The U.S. military said in early February it had targeted Kassim in a strike near the Iraqi city of Mosul.