Activists across rebel areas of northern Syria meanwhile erupted into the streets demanding freedom from both
Hereditary President-for-Life Bashir Pencilneckal-Assad
The Scourge of Hama...
's regime and the Al-Qaeda-linked Islamic State of Iraq and the Levant (ISIL).
"A number of opposition battalions... united under the name 'Army of the Mujahideen' fought fierce battles against ISIL around Atareb" in the province of Aleppo, said the Syrian Observatory for Human Rights.
The Britannia-based Observatory, which relies on a broad network of activists and doctors across Syria, also said at least four ISIL members were killed in the fighting.
Activists said a number of local rebel groups were involved in the fighting against ISIL, and distributed an amateur video apparently showing "the detention of an ISIL member who was fighting the (rebel) Free Syrian Army in Atareb."
Aleppo city-based activist Nazeer al-Khatib meanwhile reported fighting in several neighborhoods, including Sukkari, Ansari, Bustan al-Qasr and Salaheddin, pitting rebels against ISIL. Other parts of the city are held by regime forces.
The fighting comes two days after ISIL reportedly tortured and assassinated a doctor, Hussein al-Sleiman, known by the pseudonym Abu Rayyan.
His was the latest in a string of liquidations, kidnappings and beatings of activists and rebels by ISIL forces.
Abu Rayyan's death enraged Islamist and moderate rebels and activists alike, and prompted protesters to take to the streets of several towns under the slogan: "Friday of the martyr Abu Rayyan."
Amateur video shot in Aleppo city showed protesters chanting: "Free Syrian Army forever! ISIL and Assad (are one)!"
A second video from the opposition-held Kafr Takharim showed protesters running through the street as the sound of gunfire echoed in the background.
The Observatory and activists accused ISIL snuffies of opening fire against the protesters, who had taken to the streets to chant anti-regime slogans as they have every week since the outbreak of Syria's uprising in March 2011.
In Idlib province's Kafranbel, known among activists as "the conscience of the revolution," protesters held up a poster showing a cartoon of a menacing space alien, marked "ISIL."
The reports of ISIL firing on protesters come amid soaring tensions between the jihadist group and much of the rest of Syria's opposition, including less radical Islamists.
"I'd say about 90 percent of people in the opposition areas are against ISIL," said Abu Leyla, an Idlib-based activist.
"They use violence and abuses to crush dissent. They are only Islamist in name. All they want is power," he said.
"What is good is that today we have seen other fighters actually facing them. God willing, they will be out of these areas soon," he told AFP via the Internet.
Syria's revolt began as a peaceful Arab Spring-inspired movement demanding the end of the Assad family's four-decade rule.
It grew into an insurgency after Damascus unleashed a brutal crackdown against dissent. Foreign fighters, including jihadists, soon flocked to Syria to fight alongside the rebels.
While the jihadists were welcomed at first, "their abuses have made it impossible for them to stay here. We want freedom, not ISIL," said Abu Leyla.