Al-Qaida militants battled fighters linked to the Western-backed opposition along with Kurdish gunmen in Syrian towns along the Turkish border on Friday, in clashes that killed at least 19 people, activists said.
The violence is part of an outburst of infighting among the myriad rebel groups opposed to Syrian President Bashar Assad for control over prized border areas. Islamic extremist fighters and more mainstream rebels are increasingly turning their guns on each other in what has effectively become a war within a war in northern and eastern Syria, leaving hundreds dead on both sides.
Turkey has been a staunch supporter of the rebels seeking to topple Assad, and has allowed the flow of weapons, men and supplies through border crossings into Syria.
In an interview with Turkey's private Halk TV, Assad said Turkey will pay a "high price" for allowing foreign fighters to enter Syria from its territory. "You cannot hide terrorists in your pocket. They are like a scorpion, which will eventually sting you," Assad added.
The interview, broadcast late Thursday, was the latest given by the Syrian president to foreign media as part of a charm offensive in the wake of the Russian-brokered deal that averted the threat of a U.S. airstrike over an August chemical weapons attack that killed hundreds of people.
Assad said it was still too early to say whether he'll run for re-election next year, but suggested he would refrain from seeking a third term — if he feels that is what most Syrians want him to do. He said "the picture will be clearer" in the next four to five months because Syria is going though "rapid" changes on the ground.
"If I have a feeling that the Syrian people want me to be president in the coming period, I will run for the post," Assad said. "If the answer is no, I will not run and I don't see a problem in that."
Assad has been president since 2000. He took over after the death of his father and predecessor, Hafez Assad, who ruled for three decades.
Syria's opposition wants Assad to step down and hand over power to a transitional government until new elections are held.
A spokeswoman for the U.S. State Department called it "really unfathomable" that Assad would even contemplate running again.
"If he really were to follow the wishes of the Syrian people, he would go," Marie Harf said.
"This is a process that will take time," she added. "But I think the notion of a brutal dictator who's killed so many of his own people claiming to have any opportunity to run for additional elected office is really actually quite offensive."
The infighting between rebels and the increasingly domineering role played by foreign fighters in the civil war has played into the government's line that it is fighting extremists, not a popular uprising.
Activists said heavy fighting continued Friday in the town of Azaz near the Turkish border between al-Qaida militants from the Islamic State of Iraq and the Levant and fighters linked to the Western-backed Free Syrian Army group.
An activist affiliated with Syrian rebels, who identified himself as Abu Raed, said one fighter from the Northern Storm brigade involved in the fighting against ISIL was killed in Azaz. It was unclear what the overall death toll was.
He said the infighting was leaving Syrian rebels clashing on two fronts.
"The best solution is a peaceful one. Otherwise we will have a river of blood, from all of us. It won't end, and it won't stop," he said, speaking from near Azaz via Skype.
ISIL fighters also battled Kurdish forces around the town of Ras al-Ain in Syria's Kurdish-dominated north, said a Kurdish activist, Bassam al-Ahmed, in the nearby town of Hassakeh.
The Syrian Observatory for Human Rights said 14 fighters from ISIL and the al-Qaida-linked Jabhat al-Nusra group and four Kurdish gunmen were killed.
In Damascus, a team of international weapons experts in Syria was out in the field on its fourth day of work in the country. Their mission — endorsed by a U.N. Security Council resolution last week — is to scrap Syria's capacity to manufacture chemical weapons by Nov. 1 and to destroy Assad's entire stockpile by mid-2014.
The Organization for the Prohibition of Chemical Weapons said Friday that Syria had submitted information about its program. Without elaborating in the statement late Friday, the Hague-based organization said its executive council would address the issue on Tuesday.
Associated Press writer Diaa Hadid in Beirut contributed to this report.