The global chemical weapons watchdog on Thursday blamed the ISIS terrorist group for a 2015 attack on the Syrian town of Marea in which sulfur mustard was used.

The Organisation for the Prohibition of Chemical Weapons (OPCW) underscored previous reports by the body that mustard agents were used in the attack near Syria's border with Turkey.

"There are reasonable grounds to believe that units of the Islamic State in Iraq and the Levant (ISIL) were the perpetrators of the chemical weapons attack on 1 September 2015 in Marea, Syria," said the organization, which is based in The Hague.

"The chemical agent was delivered using one or more artillery guns," it added in a statement.

It said it had identified four individuals as perpetrators, but did not name them.

At least 11 people were injured in the attack on the town located in Aleppo province near the Turkish border. The town came under shelling from areas under IS control on September 1 and 3 that year.

"Upon impact, at least six projectiles leaked a black, viscous substance with a 'pungent' and 'garlic-like smell, the OPCW said.

"At least 11 individuals who came into contact with the liquid substance experienced symptoms consistent with exposure to sulfur mustard," it added.

The investigation team report comes following a 2022 finding by an OPCW fact-finding mission that sulfur mustard was used.

A 2015 report found that mustard gas was used in an attack on Marea on August 21, 2015, killing at least one infant.

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