Kurdish authorities claim to have evidence which shows Islamic State used weaponised chlorine gas against Peshmerga fighters in January.

The Security Council of the Kurdish region said soil and clothing samples showed traces of chlorine after an IS car bombing attempt.

Analysis of the samples showed they "contained levels of chlorine that suggested the substance was used in weaponised form".

The allegation has not been independently verified.

Peter Sawczak, spokesman for the Organisation for the Prohibition of Chemical Weapons, said: "We have not had a request from Iraq to investigate claims of use of chemical weapons in Iraq, and the OPCW cannot immediately verify the claims."

The use of chlorine as a chemical weapon dates back to World War One.

The substance was banned under the Chemical Weapons Convention in 1997.

Chlorine has been used "systematically" in the civil war in neighbouring Syria, an OPCW fact-finding mission found last year.

The Kurdish authority said in a statement that the car bombing attempt happened on 23 January on a highway between Mosul and the Syrian border.

Peshmerga fighters fired a rocket at the car, killing the driver.

About a dozen Peshmerga fighters later experienced symptoms of nausea, vomiting, dizziness or weakness.

Video footage and photographs of the incident were sent to the Reuters news agency.

In some of the photographs, several canisters are seen lying on the ground.

The White House said in a statement it could not confirm the allegations but found them "deeply disturbing" and was monitoring the situation "very closely".

A US defence official said the use of chlorine as a weapon was a possible sign of "growing desperation due to the pressure being applied by coalition air power and Iraqi ground forces".

Iraqi Kurds were the victims of the deadliest chemical attack of modern times when Saddam Hussein's air force bombed the town of Halabja in 1988, gassing at least 5,000 people to death.
(Sky News)