The strikes on Tuesday targeted the Daesh-held city of Shaded in the countryside of al-Hasakah, said the so-called Syrian Observatory for Human Rights.
The UK-based group said the death toll will likely rise due to the number of critically wounded people, Xinhua reported.
The US-led coalition has been striking Daesh positions in Syria for over a year, but Syrian officials have been slamming the strikes as "ineffective," while hailing the air support by the Russian air force, a main ally of the Syrian army in recent crushing offensive against militant groups across the country.
The Syrian army has also been advancing in northern Aleppo.