Islamic State reportedly launched a chemical attack on a unit of Kurdish self-defense close to Sinjar in northern Iraq. Up to 30 Kurdish fighters were affected by what is believed to be mortar shells loaded with a chemical substance, presumably chlorine.

Medical officials at Dohuk hospital saw nine Kurdish fighters admitted to their facility with symptoms of heavy chemical-weapons poisoning last Friday, such as corrosive burns of the upper respiratory tract, vomiting and itching, the Associated Press reports.

Director of Dohuk hospital, Dr Afrasiab Mussa Yones said further analysis is necessary, but the initial symptoms suggest chlorine had been used. Samples taken from the troops' clothes would be sent for analysis, he said.

Kurdish military Colonel Lukhman Kulli Ibrahim told AP that following the mortar attack he lost consciousness. When he came to, he felt his chest and eyes burning.

Earlier this week, the Organization for the Prohibition of Chemical Weapons (OPCW) acknowledged that Islamic State (IS, former ISIS/ISIL) used mustard gas on Kurdish forces in Iraq last August. Lab tests came back positive for the substance.

#ISIS used mustard gas against Kurdish forces in Iraq – chemical weapon watchdog https://t.co/xfT87KU1wkpic.twitter.com/TJ4OhEDHRN — RT (@RT_com) February 16, 2016

Last week, US Central Intelligence Agency director John Brennan warned that IS had used chemical munitions in battle and may have access to chemical agents.

“We have a number of instances where ISIL has used chemical munitions on the battlefield,” the CIA chief told CBS. “There are reports that ISIS has access to chemical precursors and munitions that they can use.”

READ MORE: ISIS used chemical weapons, may have more - CIA chief

In November 2015, AP cited Iraqi and US officials, saying Islamic State has created a special branch to develop chemical weapons. The terrorist group is using scientists from Iraq and Syria as well as other countries in the region.