At least 13 people were killed by a car bomb in the northern Syrian border town of Tal Abyad, Turkish authorities said.
Turkey's defence ministry said at least 20 others were wounded by the blast.
Turkish troops and Turkey-backed rebels last month took control of Tal Abyad and other border towns from Kurdish forces, after US troops - who were protecting the Kurds - pulled out.
Pro-Turkey fighters and civilians were among the dead on Saturday, according to a UK-based monitoring group.
The monitor, the Syrian Observatory for Human Rights, said more than 30 people were also injured in the blast. Turkey's defence ministry accused a Syrian Kurdish militia group, the People's Protection Units (YPG), of planting the bomb. No group immediately claimed responsibility.
What is Turkey doing in northern Syria?
Turkey's military invaded the Kurdish-held border areas in northern Syria immediately after US forces were withdrawn. Turkey has a longstanding enmity with the Kurds and wants to push back the YPG from its border.
Turkey claims the YPG is a "terrorist" offshoot of the outlawed Kurdistan Workers' Party (PKK), which has fought an insurgency against the Turkish state since 1984.
Turkish forces have created a 120-kilometre (75-mile) "safe zone" between Tal Abyad and the town of Ras al-Ain, pushing the YPG out of the area. Turkish troops on Friday began joint patrols with Russian forces.
US President Donald Trump faced widespread international criticism for his decision to remove American troops from the area, leaving Kurdish forces - which allied with the US in the fight against the Islamic State (IS) group, suffering heavy losses - outgunned by the Turkish military.
Tens of thousands of people fled their homes in October in border towns in northern Syria, including Tal Abyad and Ras al-Ain, as Turkish forces pushed into the area.
What about the IS members Turkey has detained?
Turkey says it will send members of IS that it has so far detained back to their home countries.
Tens of thousands of IS fighters and their family members were taken captive by Western-backed forces in north-eastern Syria.
Turkey is now holding a number of those who have escaped, including British and Dutch nationals, after launching its incursion into northern Syria.
The country's interior minister criticised the reluctance of European countries to repatriate nationals who had been taken prisoner while fighting for IS in Syria.
"We are not a hotel," Suleyman Soylu said. "That is not acceptable to us. It's also irresponsible."
He vowed to ensure they were sent back to their home nations.