A new front is emerging in Syria's war, as mainstream rebels come to blows with jihadists, endangering their common goal of ousting Bashar al-Assad's regime.
Ever since Al-Qaeda front group the Islamic State of Iraq and the Levant (ISIS) appeared on the battlefield, tensions between the Free Syrian Army (FSA) and jihadists have soared, sparking firefights, kidnappings and assassinations.
On Friday, after ISIS seized the northern border town of Azaz, the opposition National Coalition for the first time publicly condemned attacks by jihadists.
"The Coalition condemns the aggressions against the forces of the Syrian revolution and the repeated disregard for the lives of Syrians, and considers that this behaviour runs contrary to the Syrian revolution and the principles it is striving to achieve," it said.
The statement came after ISIS seized Azaz on the border with Turkey from FSA hands.
Problems between the FSA and ISIS are not only over control, but also about vision.
While the FSA is fighting to establish a democratic state in Syria, the aim of ISIS is to create and rule over an Islamic state.
On some front lines, they have fought side by side against Assad's forces but in other areas they have earned a fearsome reputation.
Although ISIS has some local support, its opponents blame its influence on Western countries that support the revolt, but which have stopped short of providing them with military aid.
ISIS, in turn, also fears that some rebel groups have been paid off by the West to confront them.
The West has repeatedly expressed fears that the rebel ranks are too divided, and that any weapons supplied to the FSA may end up in the hands of Al-Qaeda.
While tensions between fighters have been mostly localised, the Azaz fighting was the latest in a string of armed confrontations since ISIS surfaced earlier this year.
"There has been a gradual suggestion in recent weeks that some core moderates are beginning to feel aggrieved by (ISIS's) increasing influence, and recent clashes underline this," according to Charles Lister, an analyst at IHS Jane's Terrorism and Insurgency Centre.
"A series of clashes in several northern and eastern provinces between jihadists and moderates in recent days suggests that these tensions are coming out into the open," he added.
While Al-Qaeda supporters accuse the FSA of "heresy" and subordination to its Western backers, locals call the jihadists "collaborators" who play into Assad's hands.
Activists say that public executions and kidnappings of civil activists by ISIS have raised resentment among the very same people whose support it needs most.
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"ISIS is infiltrated by Assad's secret services, which have a history of dealing with Al-Qaeda," said Ibrahim al-Idelbi, spokesman for the Ahfad al-Rasul rebel brigade.
Activists have frequently accused the regime of setting free detainees held on terrorism charges at the start of the anti-Assad revolt, in order to sow chaos.
"ISIS has a blacklist of high-ranking (rebel) officials and revolutionary leaders they want to assassinate," Idelbi told AFP via Skype.
Last month, Ahfad al-Rasul openly clashed with ISIS in the northern city of Raqa, Syria's only provincial capital to have been lost by the regime.
Earlier in the summer, clashes between local rebels and ISIS fighters erupted in the northwestern province of Idlib.
And in coastal Latakia, ISIS was accused of murdering Abu Baseer, a popular rebel leader.
Speaking to AFP in the northern city of Aleppo, a local cleric said ISIS was getting stronger only because the West has failed to adequately help the rebels.
"We didn't invite them to come to Syria... But if the United States and the West don't help us against Bashar, we will have to accept help from anyone who shares our goal," said Abu Mohammed.
"Al-Qaeda don't help the Syrians, they also kill us," he added, echoing the fear of many Syrians in rebel-held territory of the dangers posed by ISIS.
Fear of ISIS, coupled with the FSA's poor funding, has led some rebels to take even more radical steps to protect themselves against ISIS advances.
"There's no more FSA (here). We are all Al-Qaeda now," said one rebel leader in Raqa whose men have joined Al-Nusra Front.
Although Al-Nusra shares a jihadist philosophy and ties to Al-Qaeda, it split from ISIS in spring.
"Al-Nusra is fighting to bring down the regime, while ISIS fights to bring down the FSA," one Al-Nusra new recruit told AFP via the Internet.
ISIS "are not coming to fight the regime. They are here to kill anything that moves".
A high-ranking security source meanwhile said the in-fighting was "positive" for Assad's regime.
"The fighting will increase in the coming days," he predicted.
"Conflict among the Syrian people's enemies means terrorism will end sooner," he added, using the standard regime term for the anti-Assad rebellion.