By Alexander Dziadosz and Stephen Kalin
BEIRUT (Reuters) - Al Qaeda-linked fighters fought rival Syrian rebels near the border with Turkey on Wednesday, activists said, in an outbreak of violence driven by the divisions between factions battling President Bashar al-Assad.
The fighting illustrates the volatile situation in Syria as a team of chemical weapons experts start the process of eliminating Syria's chemical weapons stockpile, with inspections expected to begin next week.
The al Qaeda-linked Islamic State of Iraq and the Levant (ISIL) took control of the northern border town of Azaz last month, kicking out rival rebels and prompting Turkey to shut the crossing about 5 km (3 miles) away.
ISIL, which wants to merge Syria into a larger state ruled by Islamic law, has maintained control of the town since then and clashes have periodically erupted between it and fighters of the Northern Storm brigade that they had expelled to its outskirts.
Activists said the latest fighting broke out on Tuesday night after a deadline ISIL had set for Northern Storm fighters to surrender their weapons came to an end.
"There are very fierce clashes on the outskirts of Azaz. ISIL cut all roads leading to Turkey and the situation is very tense," said one rebel source, speaking from Turkey.
Another activist from Azaz said ISIL had seized two checkpoints and a base from Northern Storm and had advanced toward the border. He said some ISIL fighters had been killed, but he did not know how many.
The Syrian rebels have been undermined by infighting, partially over conflicting ideology, but more often over territory, spoils of war and control of resources and smuggling.
The Syria conflict started as a peaceful protest movement against four decades of Assad family rule but turned into a full-scale war after a government crackdown. More than 100,000 people have been killed.
ISIL SAYS WRONGED
An activist in Azaz, Jamal Yusuf, said the border closure had made it harder for people to flee. The crossing was a lifeline for rebel-held northern areas, allowing refugees out and supplies in.
"People don't want either of them. They don't want ISIL and they don't want Northern Storm. We're saying to them, 'Please leave us'," he said.
ISIL includes a larger number of foreign fighters than other hardline Islamist brigades fighting in Syria and is viewed with suspicion by some other, less ideologically rigid rebel groups.
In an audio message this week, ISIL said its image was being distorted by a "widespread media campaign" against it that was trying to stir strife by blaming it for conflicts and ignoring its military victories or giving credit to other groups.
The message accused the Northern Storm brigade of "opening a front" against them in the Azaz area and of conspiring with "the American pig, John McCain" to fight against the Islamists.
McCain, a Republican U.S. senator who has called for U.S. military aid to rebels, visited Azaz in May and was photographed alongside Northern Storm fighters.
"A CAUSE FOR OPTIMISM"
Divisions among the rebels and the influence of hardline Islamists such as ISIL have made Western powers more reluctant to intervene in the 2-1/2-year-old conflict.
The United States threatened a military strike against Assad after an August 21 sarin gas attack in Damascus that Washington blamed on the government, but backed away after Damascus agreed to eliminate its chemical weapons stockpiles.
A team of chemical weapons experts charged with starting the process of verifying and eliminating the weapons arrived in Syria on Tuesday for the U.N. Security Council-endorsed mission.
Russia's envoy to the United Nations, Vitaly Churkin, told Russia's RT television they would begin inspections on Monday.
"Now the focus is on concrete actions for the destruction of chemical weapons in Syria. How fast work in this direction is going is a cause for optimism," he said.
Russian President Vladimir Putin said global powers are "on the right track" with the plan, which has rekindled efforts to convene an international conference to solve the conflict.
Most of the deaths in Syria's conflict have resulted from fighting with conventional weapons. The death toll still regularly climbs over 1,000 a week.
On Wednesday, fighting continued in provinces across Syria, with clashes, shelling and air strikes reported near Damascus, in the southern province of Deraa, the central Hama and Homs regions, and Aleppo and Idlib in the north.
(Additional reporting by Dasha Afanasieva in Istanbul and Steve Gutterman in Moscow; Editing by Angus MacSwan)