The same day the United States and Russia announced a plan to disarm Bashar al-Assad of his chemical weapons, a fresh round of fighting erupted along the Syria-Iraq border. This time, it was rebel versus rebel—specifically, al Qaeda–linked rebels against the more moderate elements of the opposition.

Mahmoud al-Aboud, commander of the eastern front for the Free Syrian Army, told The Daily Beast on Sunday in a Skype interview that the fighting began Saturday with a car bomb. Killed in the attack, said Aboud, was the brother of Saddam al-Gamal, a local commander of Allahu Akbar Brigades, a group aligned with the FSA in al-Bukamal. After the bombing, Gamal’s men launched a counterattack with small arms fire that killed four fighters in the opposing rebel group.
The five military councils associated with the FSA have clashed with fighters from the two main al Qaeda affiliates in Syria, al-Nusra and the Islamic State of Iraq and the Levant, in recent months. (The two al Qaeda affiliates also have fought each other in the same period in an apparent power struggle.)
But this weekend’s clashes, which came after a September 12 message from al Qaeda leader Ayman al-Zawahiri instructing his followers in Syria not to collaborate with the FSA councils, could mark a more violent stage for the opposition’s fractured ranks. “I think this message means al Qaeda forces are willing to take this fight against us into the public,” Aboud said. “I think this is happening now because there is a political vacuum.”
The FSA, which has received some nonlethal aid from the United States as well as weapons from such American allies as Saudi Arabia, has never collaborated with al Qaeda–linked forces in Syria against the Assad regime, Abboud said. But he also said his group focused on attacks against the regime and not fighting al Qaeda in the field. “Originally the supreme military councils did not want to fight any other rebel forces until the regime fell,” he said. “We were forced to do this.”
Laith Alkhouri, a senior analyst at the counterterrorism consulting firm Flashpoint Global Partners who monitors jihadist and local media coverage of the Syrian conflict, said the fighting was reported by the al-Bukamal network, a local news outlet that covers fighting in Syria in and around the eastern Syrian town of the same name. The Associated Press also reported on the fighting over the weekend
“Local mainstream rebel factions comprised of Syrian fighters who are not looking for a caliphate are clashing with al Qaeda–linked groups who want to seize control of these areas,” Alkhouri said. As al-Bukamal is “an area that ignited the Syrian revolution, it’s becoming very important for al Qaeda to establish a presence there.”
Last week Rep. Mike Rogers (R-MI), chairman of the House Permanent Select Committee on Intelligence, told a conference of intelligence contractors that he estimated 10,000 jihadists had gathered in eastern Syria. In an interview with The Daily Beast, Rogers said the United States knew that al Qaeda operatives in Syria and other al Qaeda leaders viewed the area along the Syria-Iraq border as a potential safe haven.
Rogers said he did not doubt the FSA wanted to target al Qaeda after the Assad regime fell. “They believe when this is done they can mop up al Qaeda units,” he said. “That candidly does not fit the history of how al Qaeda operates in the world. I think they underestimate their size and strength in the east.”
Aboud said he was aware of the growing power of al Qaeda in eastern Syria. “I already sent a warning message to the U.S. government that the extremist elements are gaining ground,” he said. “We are sending similar messages now. If we do not get support now, the coming war between us and al Qaeda will not have a good result.”