ISIS militants have fired a rocket in northern Syria that caused symptoms of “chemical gas” exposure in 22 Syrian rebels, state media cited Turkey’s military as saying on Sunday.

According to the state-run Anadolu agency, the ISIS rocket attack happened in the Haliliye area, however the exact place of the attack was not specified.

The main targets were Turkey-backed rebels who have been recently besieging the ISIS-controlled town of al-Bab, a major goal in Ankara’s “Euphrates Shield” operation to push the jihadists away from the Syrian side of the Turkish border.

“Twenty-two rebels were observed to have symptoms of being exposed to chemical gas in their eyes and bodies as a result of the rocket fired by ISIS,” media reports quoted the army statement.

The rebels were transferred to a hospital in Turkey’s border province of Kilis on suspicion of chemical poisoning, according to Hurriyet newspaper.

In the last 24 hours around al-Bab, Turkish jets have destroyed four ISIS targets in the Anifah region, and one Turkey-backed Syrian rebel has been killed and 14 wounded in clashes, the military stated.