“The Assad regime must know that it will be held to account for such use in the international community,” Kerry said, noting that the report raises “especially troubling concerns that continued chemical attacks on the Syrian people by the regime could occur.”

The OPCW released its report on Wednesday. While it does not assign responsibility, Kerry pointed to witness accounts of helicopters being used in the attacks, which would indicate the Assad regime carried them out.

The OPCW said earlier this month that a toxic chemical, almost certainly chlorine, was used “systematically and repeatedly” as a weapon in attacks on villages in northern Syria earlier this year.