Turkey-backed Free Syrian Army (FSA) fighters showed signs of chemical exposure after an attack carried out by Daesh terrorists in northern Syria, military sources said on Sunday.

According to sources, the terrorists used chlorine gas in its first reported chemical attack against the FSA. A total of 22 FSA fighters were said to be affected in the attack.

Abdullah Ağar, a security expert speaking to NTV news channel said that the terrorists are thought to have obtained chemical weapons from the Iraqi and Syrian armies.

He continued by saying that such attacks aim to slow down Turkey's Operation Euphrates Shield, but necessary measures, such as equipping opposition fighters with gas masks, may be taken if such attacks continue.

Meanwhile, one FSA fighter has been killed, with 14 others wounded in clashes while Turkish jets destroyed four Daesh terrorist targets in the Anifah region, sources said.

Operation Euphrates Shield, which began on Aug. 24 with the support of the Turkish Armed Forces (TSK), is aimed at bolstering border security, backing up coalition forces and eliminating the threat posed by terror organizations, especially Daesh.

Operations by the TSK, which has been actively fighting Daesh, have significantly contributed to the ongoing efforts of U.S.-backed international coalition against the terror group.