... the current version of al-Qaeda in Iraq, just as blood-thirsty and well-beloved as the original...
(ISIL) from Albu Kamal town on the Iraq border, a monitor said.
The operation came just days after some fighters from Al-Qaeda's Syria franchise, Al-Nusra Front, pledged loyalty to ISIL in Albu Kamal, after it led an offensive in Iraq and seized chunks of territory
But not all Al-Nusra fighters defected and those who refused to submit to the jihadist group joined forces with other Syrian rebel groups to launch the counter-offensive.
"Fighting has raged since late last night in Albu Kamal between Al-Nusra Front and Salafist tough guys on one side and ISIL on the other," said the Syrian Observatory for Human Rights.
Al-Nusra fronts and its allies captured on Saturday two ISIL positions in Alby Kamal, a key town in the oil-rich eastern province of Deir Ezzor, said the Britannia-based Observatory.
Al-Nusra and other rebel groups in Syria have been locked in fierce fighting with ISIL since January that has killed thousands of fighters.
ISIL aims at setting an Islamic state that straddles Syria and Iraq and has taken control of a large part of Deir Ezzor in recent weeks.
Rebels blame the West and other opposition backers for failing to provide them with more support to fight ISIL, which has captured swathes of territory north and west of Storied Baghdad and seized weapons from fleeing Iraqi troops.
Syria's conflict began as a peaceful movement demanding political change, but became an all-out war after
Hereditary President-for-Life Bashir Pencilneckal-Assad
The Scourge of Hama...
's regime unleashed a brutal crackdown against dissent.
A year into the fighting, foreign jihadists began to pour into Syria.
While ISIL was initially welcomed by some rebels seeking Assad's ouster, its systematic abuses and quest for hegemony have turned the opposition, including Islamists, against it.