“Thousands of foreign terrorists traveled to Syria over the past several months to wage jihad, or holy war, in what U.S. officials say is fast becoming a new international terror training ground.
Most of the foreign terrorists are fighting for the al Qaeda-linked group the al-Nusra Front and are coming from around the world, mainly from Saudi Arabia, Iraq, Libya, and Tunisia, by crossing the Syrian border with Turkey. The al-Nusra Front is the most well organized and ideologically motivated armed opposition group after the secular Free Syrian Army.”
Source: Syria is jihad central: 6,000 terrorists flood new al Qaeda training ground – Washington Times