The executions have taken place "in the last 24 hours" in Buyir northwest of Manbij which is mostly populated by Syrian Kurds, the so-called Syrian Observatory for Human Rights said on Friday.
According to the London-based monitor, Daesh seized control of several villages northwest of Manbij on Thursday from the Syrian Democratic Forces, a coalition of Arab and Kurdish militants which are supported by the US.
Buyir lies between the Turkish border and Daesh's self-proclaimed capital of Raqqah city in Syria.
