BEIRUT: Rebel groups from northern and eastern Syria demanded aid Wednesday from the country's exiled opposition to allow them to fight against the jihadist Islamic State of Iraq and Greater Syria (ISIS) group.
"We, the leaders of the brigades and battalions... give the National Coalition, the (opposition) interim government, the (rebel) Supreme Military Council and all the leading bodies of the Syrian revolution a week to send reinforcements and complete aid," the statement said.
"Should our call not be heard, we will lay down our weapons and pull out our fighters," it added.
The statement comes three days after ISIS declared the establishment of a "caliphate" straddling Syria and Iraq, referring to an Islamic system of rule that was abolished nearly 100 years ago.
"Our popular revolution (against Syrian President Bashar Assad)... is today under threat because of the Islamic State of Iraq and Greater Syria (ISIS), especially after it announced a caliphate," said the statement.
ISIS first appeared in Syria's war in late spring 2013. It has since taken control of Raqqa in northern Syria, much of Deir al-Zor in the east, and parts of Aleppo province.
The factions that signed the statement are local rebel groups based in the areas where fighting against ISIS has been most intense, and which are now under ISIS control.
Rebel groups from those areas have frequently complained of poor funding, despite their opposition to ISIS.
Some Syrian rebels seeking Assad's ouster initially welcomed the war-hardened ISIS fighters among their ranks.
But their systematic abuses and quest for hegemony in opposition-held areas eventually turned the rebels against them and their project.
ISIS has kidnapped thousands of Syrians, many of them political activists and rebels, and carries out summary executions in areas under its control.
The group has been bolstered in recent weeks by an offensive it spearheaded in neighboring Iraq, capturing large swath of territory as well as heavy weapons seized from fleeing Iraqi troops.
Syria's war began as a popular revolt demanding Assad's ouster, but morphed into a war after his regime unleashed a brutal crackdown against dissent.
Many months into the fighting, jihadists started to pour into Syria, and in January 2014, the country's rebels including Islamists launched a major offensive against ISIS.