Ankara said Thursday it had uncovered a mass grave containing dozens of bodies in a Turkish-held region of northern Syria, accusing a US-backed Kurdish militia of the killings.
Turkey and its Syrian proxies have seized control of territory inside Syria since 2016 in military operations against the Islamic State (IS) and the YPG Kurdish militia.
The governor of Turkey's Hatay province on the border with Syria told reporters a mass grave was found with 61 bodies in the Afrin area.
"This is a crime against humanity," Rahmi Dogan said, blaming the YPG, which is backed by Washington.
"I think the number of bodies recovered will rise," he added, after the Turkish defence ministry initially put the number at 35 on Wednesday.
Images on Turkish television showed officials in hazmat suits surrounded by what appeared to be bodies in bags.
Dogan said Turkish authorities believe the dead were civilians executed by the YPG days before Turkey launched its so-called Olive Branch operation in 2018 to capture Afrin.
AFP was unable to independently verify the claims.
Turkey accuses the YPG -- a force backed by Western militaries against IS -- of being a "terrorist" offshoot of the outlawed Kurdistan Workers' Party (PKK).
The PKK, blacklisted by Ankara and its Western allies, has been waging an insurgency against Turkey since 1984, in a conflict which has killed more than 40,000 people.