A car bomb killed 19 people, 13 of them civilians, in the Turkish-controlled town of Al-Bab in northern Syria on Saturday, a war monitor said.
The bomb, which struck a bus and taxi station in the town, also wounded 33 people, some of them seriously, the Britain-based Syrian Observatory for Human Rights reported.
Turkey and its Syrian proxies control several pockets of territory on the Syrian side of the border as a result of successive incursions in 2016-17, 2018 and 2019.
There was no immediate claim of responsibility for the bombing but the Observatory said there had been persistent security incidents in the town since its capture by Turkish troops from the Islamic State group in February 2017.
The town, some 30 kilometres (20 miles) northeast of Syria's second city Aleppo, was one of the westernmost strongholds of the jihadists' self-styled "caliphate" which was finally eradicated by US-backed Kurdish forces in eastern Syria in March.
Turkey blamed the car bombing on the Kurdish People's Protection Units (YPG) against whom it launched a new invasion further east last month.
Kurdish fighters "continue to target innocent civilians using the same methods as Daesh," the defence ministry said on its official Twitter account using another acronym for IS.
There was no immediate reaction from the YPG, seen by Ankara as a "terrorist offshoot" of the Kurdistan Workers Party which has fought an insurgency inside Turkey for the past 35 years.
The latest Turkish invasion, which was aimed at creating a buffer zone the whole length of the border, sparked an outcry in the West because of the key role the YPG played in the US-led campaign against IS.
It paused after Turkey struck a truce deal with Russia, the main supporter of the Syrian government, to jointly patrol the border area and oversee the withdrawal of Kurdish fighters from a new Turkish-controlled pocket between the towns of Tal Abyad and Ras al-Ain.
Turkish-backed Syrian fighters take down a black Islamic State group flag during their capture of the northern town of Al-Bab in February 2017