The Conflict Armament Research (CAR) group and Sahan Research said in a statement Friday that ISIS targeted Iraqi Kurdish peshmerga with a projectile filled with a chemical agent on June 21 or 22.

The organisations also documented two such attacks against Kurdish fighters from the People's Protection Units (YPG) in Syria's northeastern Hasakeh province on June 28.

The YPG said the attacks targeted the Kurdish-held Salhiya district of Hasakeh city and Kurdish positions south of the town of Tel Brak.

"Upon impact, the projectiles released a yellow gas with a strong smell of rotten onions," the YPG said in a statement on Friday.

It added that the ground around the impact sites was stained with a liquid that was green at first but turned yellow on contact with sunlight.

"Our troops exposed to the gas experienced burning of the throat, eyes and nose, combined with severe headaches, muscle pain and impaired concentration and mobility. Prolonged exposure to the chemicals also caused vomiting."

The YPG reported no deaths in the attacks and said that exposed forces subsequently recovered from their symptoms.

They added that YPG fighters had captured industrial-grade gas masks from ISIS forces in recent weeks "confirming that they are prepared and equipped for chemical warfare along this sector of the front."

CAR and Sahan Research, who conducted research in coordination with Kurdish forces, said in a joint statement that seven projectiles were fired in the Hasakeh city attack, and 17 in the attack near Tal Brak.