U.N. Secretary-General Ban Ki-moon expressed alarm at "the weakening taboo" against using chemical weapons in Syria, where the international watchdog said it is studying several recent cases of alleged use of the banned agents, according to a letter circulated Monday.
The U.N. chief said in a letter to the Security Council transmitting the monthly report from the Organization for the Prohibition of Chemical Weapons that he is gravely concerned that the use of chemical weapons could become "normalized in this or any conflict, present or future."
"It is imperative that those responsible for the use of chemical weapons should be held accountable," Ban told the council in the letter.
The OPCW said in its report covering the period from Sept. 23 to Oct. 22 that its fact-finding mission is studying four widely reported allegations of chemical weapons use, and is investigating the alleged use of a chemical agent in Aleppo on Aug. 2 at the request of the Syrian government.
OPCW Director-General Ahmet Uzumcu said the organization's fact-finding mission continues studying all available information of alleged chemical weapons use "with a particular focus on widely reported incidents" in the Saraqib in Idlib governorate, and three incidents in the Aleppo governorate – in Aleppo city, Zubdiya, and Al Sukkari.
He did not provide details but said "the intensity of the ongoing conflict in Aleppo is a major challenge" to the mission's work.
Uzumcu said an OPCW team was sent to Damascus from Oct. 12-19 in response to the Syrian government's request to investigate the alleged use of chemical weapons on Aug. 2 in the area of Al-Awamid in Aleppo. He said it will continue to work with Syrian authorities to gather more information.
The OPCW has a mandate to carry out fact-finding missions to determine whether chemical attacks occurred in Syria, but not to determine responsibility. In September 2014, the Security Council established an international body to assign blame for chemical attacks.
That body, the Joint Investigative Mechanism, or JIM, has already determined that the Syrian government was behind three attacks involving chlorine gas and the Islamic State extremist group was responsible for one involving mustard gas.
Syria's government has been repeatedly accused by the United States and other Western countries of using chemical weapons on its own people, even after the Security Council in 2013 ordered the elimination of its chemical weapons program following an attack on a Damascus suburb that killed hundreds of civilians.
The council last year also condemned the use of toxic chemicals like chlorine after growing reports of barrel bombs filled with chlorine gas being dropped on opposition-held areas. Chlorine is widely available and not officially considered a warfare agent, but its use as a weapon is illegal.
Uzumcu said poor security has prevented the destruction of Syria's remaining declared chemical weapons production facilities. He said questions also remain over its initial declaration of its chemical holdings.
Ban retierated the need for the Syrian government and the OPCW "to work together to resolve all identified gaps, inconsistencies and discrepancies" in the declaration.