The Syrian Observatory for Human Rights said the dead in air strikes and shelling on the town of Al-Bab in the last 24 hours included 11 children.
Turkey's army, quoted by the state-run Anadolu news agency said it had killed 15 "terrorists" in air strikes, artillery fire and clashes.
Al-Bab is IS's final stronghold in the northern Syrian province of Aleppo and has come under fierce attack by Turkish forces and allied Syrian rebels in recent months.
The joint force entered Al-Bab over the weekend, and Turkish Prime Minister Binali Yildirim said Tuesday that the town had "largely been taken under control."
The Observatory however said Turkish forces had made little progress since entering the town from the west.
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Turkey began military operations in Syria in August, targeting both IS 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 from the south.
But they have yet to enter Al-Bab, instead focused on clearing IS-held territory in the surrounding countryside in recent days.
More than 310,000 people have been killed in Syria since the conflict began in March 2011 with anti-government protests.
The war has displaced over half the country's population and drawn in jihadists and international militaries.