The Kurdistan Regional Security Council in Iraq says it has evidence that shows militants of the Takfiri group, ISIL used chlorine gas in attacks against Kurdish Peshmerga forces.

The Kurdistan Regional Security Council in Iraq says it has evidence that shows militants of the Takfiri group, ISIL used chlorine gas in attacks against Kurdish Peshmerga forces.

Chlorine, a choking agent first used in the first world war, is listed in the 1997 Chemical Weapons Convention as a toxic substance banned on the battlefield.

“The analysis, which was carried out at an EU-certified laboratory, found the samples contained levels of chlorine that suggested the substance was used in weaponised form,” Kurdish officials said in a statement emailed to journalists on Saturday.

Kurdish forces said similar attacks appear to have been launched against Iraqi forces advancing in an offensive to retake the city of Tikrit. The security council says the smoke that appeared in the video was orange, a sign of chlorine gas use.

“The weapon was used as they lost control of the city,” it said in the statement, adding the group’s use of chlorine appears to be when it is “suffering heavy defeats”.

A spokesman for the Organization for the Prohibition of Chemical Weapons told Reuters that his group had received no requests from Iraq to investigate chemical weapons use and could not verify the authenticity of the security council’s claims.