Attacks using poison gas were carried out via chlorine filled rockets aimed at both rebel fighters and civilians in areas controlled by the Kurdish said the Syrian Observatory for Human Rights based in the UK.
Two groups investigating this attack confirmed that chemical weapons were used during June against a Kurdish group, which had taken a lead in the fight with ISIS militants.
In another worrisome development, the radical jihadi group was said to have come in possession of industrial grade gas masks, which suggest they are preparing and becoming better equipped to carry out more chemical warfare.
The Kurdish militia said the radical Islamist group fired makeshift projectiles armed with chemicals on June 28 at two of its positions in and around Hasaka.
The form of chemical that was used has yet to be determined, although first reports suggested the substance had been a chlorine agent.
The Kurdish organization said in a prepared statement that upon impact these projectiles has released a gas that was yellow and smelled of rotten onions.
Soldiers that had been exposed to the gas experienced burning of the eyes, nose and throat combined with muscle pain, headaches and impaired mobility and concentration, said the Kurdish group.
However, no fighters were killed due to the attack as they were transported quickly to a nearby hospital. The White House announced that it was aware of the report that chemical weapons had been used and was trying to seek more information.
The Nusra Front, an affiliate of al-Qaeda in the war in Syria has accused the Islamic State previously of setting booby traps that have barrels of chlorine.
Chemical weapons were also used by the regime in Syria. United Nations inspectors confirmed their use in August of 2013. The gas used in those was sarin.
The attacks bring back the days of Saddam Hussein the former dictator in Iraq who used nerve agents and mustard gas against the Kurds.