ISIS conducted more than 19 operations in SDF-held areas like Deir ez-Zor from September 1 to September 25 resulting in deaths and injuries, the UK-based Syrian Observatory for Human Rights (SOHR) reported.
The SDF has been the partnered ground force in Syria of the US-led international coalition against ISIS.
Civilians additionally were targeted and had money extorted by ISIS, according to the SOHR, under the pretext of collecting 'zakat,' a payment on things like goods or property, in areas controlled by the Democratic Autonomous Administration of North and East Syria (DAANES).
The monitor called the developments a dangerous escalation by ISIS cells.
Control of Deir ez-Zor province, which borders Iraq, is split between the SDF and the Iran-backed Syrian regime. It is also home to many of the country’s key oilfields, such as Omar and Conoco, which the global coalition helps the SDF to control.
Authorities in northeast Syria decreed general amnesty on Tuesday for thousands of prisoners, excluding fighters and others who have committed violence.