Soldiers from the Turkish-backed Free Syrian Army (FSA) are showing symptoms of being exposed to chemical gas following a rocket attack by Daesh, said Turkish General Staff in a statement on Sunday.
The attack targeted FSA fighters who have been fighting to liberate the Daesh-controlled town of al-Bab for the past week.
Al-Bab is a major target in Operation Euphrates Shield launched by Ankara in August to push Daesh and YPG away from the Syrian side of the Turkish border.
YPG is a Syrian wing of PKK which is listed as a terrorist organisation by the United States (US), European Union (EU) and Turkey.
Turkish General Staff said 22 FSA fighters who were observed were showing symptoms of chemical gas exposure in northern Syria's Khalidiyah region.
The Turkish military also said a clash with Daesh had left one Daesh fighter dead and 14 others injured.
Meanwhile, Turkish warplanes destroyed four Daesh targets in the Anifah neighborhood near al-Bab, also in Syria's north.