Al-Qaeda fighters of all nationalities use safe houses in Turkish border towns when crossing into Syria to join the fighting against Syrian President Bashar Assad, as well as when they leave Syria to return to their home countries.

Dozens of fighters, among them European citizens, pass through the houses for a night or two each month “through invitations from friends,” the BBC reported Saturday.

The houses were said to be located in border towns such as Reyhanli, with the route passing through them becoming more and more organized.

“There are thousands of us, literally from every corner of the world,” a French fighter – a former student – told the BBC.

According to the report, fighters belonging to the Free Syrian Army, the group that initiated the insurgency against Assad, were being increasingly pushed aside by jihadi fighters who were targeting not just Assad’s troops, but also other rebels groups.

“They told us we were not true Muslims,” one Free Syrian Army commander who was forced to flee to Turkey told the BBC. “I saw how they beat my friends with iron bars, smashed their faces with ammunition boxes and then killed them. The floor was covered with blood,” he said.

“We made the revolution for freedom and equality but the jihadists don’t want this. They’ve come to destroy Syria.”

A recent study by IHS Jane’s defense consultancy, cited by The Telegraph, found that of the 100,000 rebels fighting the regime of Bashar Assad, approximately 10,000 are jihadists linked to al-Qaeda, and another 30,000-35,000 are hardline Islamists focusing exclusively on the Syrian civil war.

In October, the leader of al-Qaeda urged jihadis in Syria to unite, an appeal likely aimed at rival affiliates of his terror network fighting there to oust Assad.

Ayman al-Zawahiri said fighters must “rise above organizational loyalties and party partisanship” and unite behind the goal of setting up an Islamic state.

Al-Zawahiri also urged Syrian regime opponents not cut deals with Western-backed and secular groups. Islamist rebels have battled with secular and Kurdish rebel groups over Syria’s border crossings with Turkey for several weeks, leaving dozens dead.

Two al-Qaeda-linked groups have emerged in Syria’s civil war — Jabhat al-Nusra and the Islamic State of Iraq and al-Sham. The first is commanded by a Syrian, the second by an Iraqi, but both are loyal to al-Zawahiri.