The Organization for the Prohibition of Chemical Weapons is condemning the use of the banned weapons in Syria.

In a statement issued Friday, the OPCW's Executive Council called on all parties identified in a joint investigation with the United Nations to immediately stop using chemical weapons and allow inspections of sites of concern in Syria.

A joint investigation by the U.N. and OPCW found that the Syrian government and the Islamic State group have both used chemical weapons and toxic chemicals as weapons in violation of international law.

The OPCW expressed its sympathy for the victims of the attacks and stressed that "every actor involved in these chemical weapons attacks should be held responsible."

The Syrian government has denied using chemical weapons.