Washington (AFP) - US Secretary of State John Kerry reaffirmed US concern Sunday over the use of chlorine gas against civilians in Syria and warned President Bashar al-Assad's regime that it would be held to account.

Kerry pointed to a report by the Organization for the Prevention of Chemical Weapons that concluded with "a high degree of confidence" that chlorine has been used systematically and repeatedly as a weapon in northern Syria.

His comments came as Damascus said it had turned over all its chemical weapons, had cooperated fully with the OPCW and adhered to the Chemical Weapons Convention.

Kerry noted that the OPCW report had cited witness reports that helicopters were used in the chlorine gas attacks, which he said "strongly points to Syrian culpability" because the rebels do not have helicopters.

The report also mentioned that there were additional attacks in August which witnesses said resembled those in which chlorine gas use was confirmed, Kerry said.

"This finding, coupled with deep concerns regarding the accuracy and completeness of Syria’s declaration to the OPCW, raises especially troubling concerns that continued chemical attacks on the Syrian people by the regime could occur," Kerry said.

"The United States is gravely concerned about the findings in this report, which point to a violation of the Chemical Weapons Convention," he said. "The Assad regime must know that it will be held to account for such use in the international community."





