AMMAN (Reuters) - A rebel group affiliated with al Qaeda overran a Syrian town near the border with Turkey on Wednesday after fighting broke out with units of the Arab- and Western-backed Free Syrian Army, opposition activists said.
Fighters from the Islamic State of Iraq and the Levant stormed the town of Azaz, 5 km (2 miles) from the Syrian-Turkish border and killed at least five Free Syrian Army members, they said.
The fighting was the most severe since tensions mounted earlier this year between the rebel factions fighting to overthrow President Bashar al-Assad.
It could pose a dilemma for the Turkish government, which has been allowing militant Islamist fighters to cross into Syria from its territory, but may not be keen to see a formidable al Qaeda presence so close to its border.
Azaz is 30 km (20 miles) north of Aleppo, once Syria's commercial and industrial hub. A frequent target for air raids and missile strikes by Assad's forces, Azaz is also adjacent to al-Salamah, a border crossing with Turkey.
Activist Abu Louay al-Halabi said the fighting broke out after the Storm of the North Brigade, a Free Syrian Army unit, resisted attempts by the Islamic State fighters to abduct a German doctor working as a volunteer at a private hospital in Azaz.
"By taking Azaz, the Islamic State is a step closer to controlling the crossing. Its objective seems to be taking over the whole countryside north of Aleppo," he said.
Opposition sources said two Free Syrian Army units, Liwa al-Fath and Liwa al-Tawhid, based in Aleppo, had sent reinforcements to the Salamah crossing to defend it against a possible al Qaeda strike.
Among those killed in the attack on Azaz was Hazem al-Azizi, an activist affiliated with the Storm of the North brigade. Better known by his alias Omar Diab, Azizi worked as a correspondent for the Shahba Press opposition media network, fellow activists said.
Activist Abdallah Tareq said the violence had undermined efforts to capitalize on the relative weakness of Assad's forces in the north of the country.
"Every rebel group is suspicious of each other and the regime has been good at exploiting it. Not only we have been seeing fighting between the Free Syrian army and al Qaeda, but also among the Free Syrian Army itself and jihadists against jihadists," he said.
To the east, opposition sources said the Islamic State on Wednesday drove out the Ahfad al-Rasul brigade, an Islamist rebel unit backed by Qatar, from the central areas of the city of Deir al-Zor on the Euphrates River, in fighting that killed six guerrillas from the two sides.
The violence in Deir al-Zor, where Assad forces still control the airport and several parts of the city, came after the Islamist State routed fighters from Ahfad al-Rasul, which is not linked to al Qaeda, from the provincial capital, Raqqa, a week ago.
Fawaz Tello, a veteran opposition activist, said the strength of al Qaeda-linked brigades stemmed from the failure of the Free Syrian Army to unite rebel units inside the country and the reluctance of Western and Arab backers of the revolt to provide Assad's more moderate foes with advanced weapons.
"The al Qaeda-linked groups seem to be fighting with everyone wherever they go. But no one is going to seriously challenge them as long as the Assad regime is in place and the opposition's pleas for advanced weapons to bring him down goes unanswered," Tello said.
"The solution to al Qaeda in Syria is to get rid of the Assad regime and then build a national force to rout it from the country."
Editing by Peter Cooney