A car bomb went off in the northern Syrian town of Afrin, on Thursday killing 13 people a monitoring group said.
The bomb was allegedly controlled by Turkish-backed rebels.
Britain-based Syrian Observatory for Human Rights said eight civilians, including two children, and four rebels were killed as well as one person who remained unidentified.
The bombing took place at an entrance to the town, where several cars were lined up for inspection and more than 30 people were injured, the observatory added.
There was no immediate claim of responsibility.
The Turkish military and allied Syrian rebel fighters launched an offensive called Operation Olive Branch on January 20, 2018, in Afrin, a mainly Kurdish enclave and they took control of Afrin in March.
Ankara regards the Kurdish fighters as terrorists.
The Turkish army controls part of the border region of northern Syria.