Turkish media have cited the country's armed forces as saying 22 Syrian rebels suffered symptoms of "chemical gas" after a rocket attack by Islamic State (IS) militants.
The reports on November 27 said the attack targeted rebels who are backed by Turkey and have been besieging the IS-controlled northern Syrian town of Al-Bab for several days.
State-run Turkish news agency Anadolu cited the Turkish military general staff statement as saying: "After a rocket was fired by [IS], 22 opposition members were observed to have been exposed in their eyes and bodies to chemical gas."
It did not say when the rocket attack took place.
Turkish media reported that Turkish emergency relief teams tested the affected rebels for traces of chemical materials at a hospital in the border province of Kilis.
The Turkish army is backing Syrian rebels in an effort to drive IS militants from the Turkish-Syrian border area and ensure there is no Kurdish militia presence.
Syria's multisided civil war is in its sixth year.