The Britain-based Syrian Observatory for Human Rights, a network of activists close to Syrian opposition monitoring the conflict, said the extremist group took five villages in Azaz district, north of Aleppo, where rebels hold an enclave host to tens of thousands of internally displaced civilians.
Daesh's news agency also reported the advance, according to the Associated Press.
Syrian rebels are anticipating a major government offensive against their position in Aleppo, Syria's largest city and once the commercial capital. Aleppo is now divided between government and rebel control.
Wednesday's advance puts Daesh in a better position to strike the towns of Marea and Azaz.
Syria's conflict began in 2011, when the rise of an armed insurgency eventually plunged the country into a full-blown civil war. The fighting has killed about 400,000 people, according to the United Nations.