Militants from the Islamic State of Iraq and Greater Syria (ISIS, also known as ISIL) faced a citywide revolt from residents of the Aleppo town of Manbij, amid reports of a harsh crackdown.

Activists from the town, one of the largest in the northern province under the control of the Al Qaeda splinter group, said that a general strike was at least “80 percent” successful, as merchants shut their shops and businesses.

There were conflicting reports as to whether ISIS fighters opened fire on town residents, who have been outraged by a campaign of arrests, harassment and summary executions it carried out in recent weeks.

Several activists said that members of ISIS sought to forcibly open a number of shops that were closed as part of the strike. The Manbij Local Coordination Committee said that at least one merchant had been detained, while gunfire was heard intermittently throughout the day.

A number of rebel groups based in the city of Aleppo announced Saturday they were launching the “Northern Earthquake” offensive to chase ISIS from its locations in northern parts of the province.