Iran, the chief regional ally of Damascus, said on Saturday there is \"proof\" Syrian rebels used chemical weapons in their conflict with the regime of President Bashar al-Assad. \"We are very concerned about information regarding the use of chemical weapons in Syria, and we strongly condemn the use of such weapons,\" foreign ministry spokesman Abbas Araqchi said, quoted by ISNA news agency. \"There is proof terrorist groups carried out this action,\" Araqchi said in reference to Wednesday\'s allegedly deadly attacks in the Damascus area, without elaborating. Iran also warned against any Western military intervention in the 29-month conflict, after the United States suggested it was weighing up such a possibility.