MOST of them avoid reporters like the plague but in "liberated" northwestern Syria, it is difficult not to run into foreign jihadist fighters, both on the front lines and at rebel bases.
"Secrecy shrouding the activities of foreign militants makes it extremely difficult to assess with any accuracy their extent, location and potential ramifications," the International Crisis Group said in a report.
But while President Bashar al-Assad's domestic foes have tried for months to downplay the impact of outsiders, "foreign militants have had more direct involvement, fighting alongside Syrian insurgents", the Brussels-based group added.
The small town of Atme on the border with Turkey serves as a hub for foreign volunteers in the 21-month insurgency that has cost tens of thousands of lives.
They cross from the Turkish city of Antakya, travelling there from far and wide to join the "holy war".
Others make their way to the Turkish border town of Reyhanli before smugglers guide them across the border to Atme, a key rallying point for foreign fighters.
One fighter, 26-year-old Anas from Algeria, was already a war veteran, having fought in his homeland's Kabylie region, east of Algiers, as well as in Kashmir.
In the Jebel Akrad mountains, four Saudi men run the online websites of Islamist groups such as the Al-Nusra Front. They live in an abandoned apartment in the town of Salma, with a rocket-propelled grenade sitting in the living room near a copy of the Koran.
Asked what they are doing in Syria, they replied: "Tourism."
At the end of November, more than 100 black-clad men from Europe and Africa gathered in front of a mosque, under a sea of black Islamic flags after a Palestinian imam had preached to locals of the benefits of their presence in the town.
