(CNN) -- The leader of an al Qaeda affiliate in Syria is calling for an end to days of bloody infighting between opposition factions, according to an online message.
Abu-Mohammad al-Jolani, leader of the al Qaeda-linked al Nusra Front, called on another al Qaeda franchise -- the Islamic State of Iraq and Syria (ISIS) -- and moderate rebel groups to implement a cease-fire after more than 270 people were killed in four days of fighting between the two opposition factions, according to the Syrian Observatory for Human Rights.
In a nine-minute audio message, al-Joulani blamed "the incorrect policies" of ISIS for "aggravating the conflict" between armed opposition factions, and urged a resolution to the conflict by calling for an immediate cease-fire and creating a Sharia council made up of all relevant groups. The criticism of a fellow al Qaeda affiliate by al Nusra Front is part of a longstanding dispute between the two that came to a head last October when al Qaeda leader Ayman al-Zawahiri called on ISIS to withdraw from Syria, a call the group refused to heed.
"The whole battlefield and all those in it from foreign to local fighters will pay the price for losing a great jihad and the (Syrian) regime will rebound after it was near disappearing," al-Joulani warns in the new message posted on online jihadist forums.
The call for a diplomatic solution appeared to fall on deaf ears as clashes intensified across Syria between rebel factions and ISIS particularly in the fabled city of Aleppo, where the recently formed Islamic Front spearheaded fighting against the predominately foreign fighting force.
"They (ISIS) have become aggressive and they have crossed the red line from trespassing to assaults to their extremist agenda," Islam Aloush, spokesman for the Islamic Front, told CNN Tuesday, referring to ISIS's radical form of Sharia law, public executions, and imprisonment of opponents as key factors that spurred the opposition to take up arms against the al Qaeda-linked group.
According to activists and seasoned observers, the backlash against ISIS by more than one rebel faction across multiple provinces overwhelmed the group that claims tens of thousands of fighters among its ranks and just weeks ago appeared the most predominant military force in northern Syria with powerful influence over the majority of population centers.
Rebels besieged at least 100 ISIS fighters at a police station used as a base by the group in the key Salheen neighborhood of Aleppo, and elsewhere in the province ISIS surrendered bases and withdrew from towns and villages, the Syrian Observatory for Human Rights said.
"ISIS cannot withstand the losses they are taking and the numbers now held as prisoner of war,"Aloush said, claiming his organization, the Islamic Front, far outnumbered ISIS. The Islamic Front boasts an estimated 40,000 fighters, making it probably the single largest rebel command, according to Aron Lund, editor of the Carnegie Endowment's Syria in Crisis website.
In Raqqah, the first provincial capital under rebel control, full-scale fighting resulted in losses for ISIS at dawn Tuesday. Just a day earlier insurgents freed at least 50 people held in an ISIS detention facility, and further to the west in the Zawiya Mountain region, rebels executed at least 34 foreigner jihadists from the group.
The infighting fueling a war-within-a-war further complicates matters for international observers such as the Office of the High Commissioner for Human Rights (OHCHR) which announced Tuesday it could no longer update the death toll for the more-than-three-year civil conflict.
"We have, of course, depended on the full and transparent cooperation and sound working methods of the various groups collecting the data on the ground. Over time there are fewer and fewer such groups still active, which brought us to a point where we felt that we are not able to produce a new detailed report," Nenad Vasic a spokesman for the OHCHR said, adding the count had stopped in early December.