The strikes hit four Daesh-controlled villages in Hasakeh province, the so-called Syrian Observatory for Human Rights said, saying the toll could rise.
It said nine Daesh fighters had also been killed in the strikes on the four villages.
The Britain-based group said the latest civilian casualties came after two days of civilian deaths in US-led strikes in Hasakeh, AFP reported.
It reported another eight civilians, including one woman, were killed in US-led strikes on another Daesh-controlled village in the province on Wednesday.
And on Tuesday, 15 civilians were killed in US-led strikes on the town of Al-Shadadi, the group said.
That brought the number of civilians reported killed in US-led strikes in Hasakeh to 38 since Tuesday.
The coaliton has rarely acknowledged civilian deaths in its campaign against Daesh.
In total, the campaign has killed more than 4,250 people in Syria, according to the Britain-based group, which relies on a network of sources on the ground.