The so-called Syrian Observatory for Human Rights said the dead in airstrikes and shelling on the town of Al-Bab in the last 24 hours included 11 children, Reuters reported.
Turkey's army, however, said it had killed 15 "terrorists" in airstrikes, artillery fire and clashes.
Turkey began military operations in Syria in August, reportedly targeting both Daesh and Kurdish fighters.
Initially, its forces advanced quickly, but they stalled around Al-Bab in December.
The town is also a key target for Syrian government forces, who had been advancing towards it from the south.