Two trials opened in France and Belgium Thursday, underscoring a worrying trend: young Europeans heading to Syria to join the ranks of Islamist fighters.
One of the trials takes place in Paris, where three young men in their '20s are accused of trying to join jihadists fighting in Syria. They were detained at a French airport in 2012 as they tried to board a flight to Turkey. They allegedly planned to head on to Syria. Two of the three deny the charges.
A similar trial opened Thursday morning in Brussels, where 19 people are suspected of having links to radical Islamist groups in Syria, and in Somalia.
While the trials reflect efforts to catch suspects before they head to Syria, experts say hundreds of others have made it. Once there, many join Islamist rebels fighting the regime of Syrian President Bashar al-Assad.
This week, U.S. intelligence officials estimated that more than 7,000 foreign militants are fighting in Syria's civil war. European experts believe that up to 2,000 of them are from Europe.
Farhad Khosrokhavar, a Paris university professor and expert on radical Islam, says many of these Europeans are idealists, who feel Europe has nothing to offer them.
"What motivates them is not so much opposition to Europe. They are not jihadists against Europe - at least not at the beginning. They are pro-Muslims," he said. "I call it the new Umma ideology - that means they have to go help other Muslims in distress and risk being repressed by autocratic regimes."
He says those who end up joining radical Islamists in Syria and elsewhere are later ideologically brainwashed to become anti-Western. In France, authorities estimate up to 700 French have joined the Syrian conflict. About 76 have returned, sparking fears of attacks at home.
Some of those hoping to join the Syrian militants are extremely young. Some are women. Two French teenagers were caught en route to Syria this month. They were taken into custody on Wednesday, in the southwestern city of Toulouse.
"The problem with these young guys is that they are immature. They are sometimes adolescents - they are between 15 and 17 or 18 years of age. The age of most of those people who go to Syria is between the age of 18 and 28," said Khosrokhavar.
European Union authorities have called on the 28-member bloc to adopt stronger prevention measures and so-called "deradicalization" programs to help stop the spread of extremism.