Two French teens have traveled to Syria to fight for an Islamist extremist group, making them what are believed to be the youngest Westerners to join the fight against President Bashar Assad.

Many American, British Western European citizens have attempted or succeeded in joining the nearly three-year-old civil war in Syria, but the 15-year-olds from Toulouse, in southern France, may be the youngest jihadists to do so.

“I’ve informed the Paris anti-terrorist prosecutor because the two boys made their intention clear that they would travel to Syria via Turkey,” prosecutor Michel Valet told Reuters.

The unnamed French boys didn’t turn up for school on January 6 and bought tickets to Syria using a family credit card, the Daily Mail reported. One of the boys’ father told a French newspaper that his son “was brainwashed online” before he decided to go to war-torn Syria.

According to Reuters, one of the boys called home earlier this week to say he was in danger and that he would not call again for a month.

President Francois Hollande said earlier this month that an estimated 700 French citizens have gone to Syria to join jihadist groups fighting the Assad regime. Of those, approximately 20 have been killed.

The western Europe-based rebels, mostly young men, are being recruited by new networks that arrange travel and comfortable lodging in the heart of rebel territory, and foster a militant form of Islam that Western security officials fear will add to the terror threat when the fighters return home.

The 11 western European countries with the biggest contingents in Syria are estimated to have some 1,200-1,700 people among rebel forces, according to government and analyst figures compiled by The Associated Press last month. That compares to estimates of 600-800 from those countries in late spring.

In March 2012, Toulouse resident Mohammed Merah shot a rabbi and three children outside a Jewish school in Toulouse. Merah confessed to the shooting before being killed by a French SWAT team after a 32-hour siege of his apartment. He had earlier traveled to Afghanistan for training with al-Qaeda. 

AP contributed to this report.