A car bomb killed 16 people including two civilians and three Turkish personnel on Thursday at a checkpoint in the Turkish-held border town of Ras Al-Ain in northeast Syria, a war monitor said.
The other 11 killed were local security forces or members of a Turkish-backed faction manning the checkpoint, the Britain-based Syrian Observatory for Human Rights said.
Twelve more were wounded, it said.
Turkey said two of its gendarmes had been killed and a further eight wounded.
Turkish forces and their Syrian proxies last year seized a 120-km stretch of land inside the Syrian border from Kurdish forces, running from Ras Al-Ain to Tal Abyad. Such bombings are common in Ras Al-Ain.