THE HAGUE -- The Syrian regime used the chemical weapon chlorine in an attack on the Idlib province town of Saraqeb in 2018, the Organisation for the Prohibition of Chemical Weapons (OPCW) said Monday (April 12), following an investigation.

The report is the second by an investigations team set up by the OPCW.

In a statement, the OPCW said its Investigations and Identification Team (IIT) "concludes that units of the Syrian Arab Air Force used chemical weapons in Saraqeb on February 4, 2018".

"The use of chemical weapons anywhere, by anyone, and under any circumstances is intolerable, and impunity for their use is equally unacceptable," said UN Secretary-General António Guterres.

"It is imperative to identify and hold accountable all those who have used chemical weapons," Guterres said.

French Foreign Minister Jean-Yves Le Drian said the evidence of chemical weapons use by the Syrian regime was "documented and irrefutable", and called for an "appropriate response" from the international community.

"Those responsible must be held accountable," said German Foreign Minister Heiko Maas.

Night-time attack

"There are reasonable grounds to believe that, at approximately 21:22 on February 4, 2018, a military helicopter of the Syrian Arab Air Force under the control of the Tiger (Nimr) Forces hit eastern Saraqeb by dropping at least one cylinder," the OPCW report said.

"The cylinder ruptured and released chlorine over a large area, affecting 12 named individuals."

OPCW investigators interviewed 30 witnesses, analysed samples collected at the scene, reviewed symptoms reported by victims and medical staff and examined satellite imagery to reach their conclusions, the Hague-based organisation said.

Symptoms "included shortness of breath, skin irritation, chest pain, and coughing", the report said.

Soon after the helicopter bombardment, foul odours filled the air, prompting residents to stay away from the stricken area, Saraqeb co-ordination committee member Mohammed al-Khalid said in the immediate aftermath of the attack.

Civil defence teams and rescuers arrived at the scene and "immediately realised toxic gases -- likely phosphorus and chlorine -- had been released", he said.

According to the civil defence (White Helmets), 12 cases of suffocation-like symptoms were recorded, with nine civilians and three civil defence members suffering from breathing difficulties.

They were treated at the scene with oxygen masks and washdowns, and transported to local medical centres for followup treatment and observation.

The OPCW said it "regrets" that the Syrian regime refused to grant access to the site, 50 kilometres south of Aleppo, despite repeated requests.

US envoy to the United Nations Linda Thomas-Greenfield on March 4 accused the regime's allies -- particularly Russia -- of seeking to stymie efforts to hold the Syrian regime accountable for its use of chemical weapons.

'Orders would be required'

The OPCW team issued its first report a year ago, in which it said Syrian President Bashar al-Assad's air force used the nerve agent sarin and chlorine in two attacks on Latamneh in northern rural Hama province in March 2017.

Despite strong objections by the Syria regime and Russia, OPCW member states voted in 2018 to set up the team to attribute blame for attacks. Previously the watchdog could only say if chemical attacks had happened or not.

Syria has continued to deny the use of chemical weapons and insists it has handed over its weapons stockpiles under a 2013 agreement, prompted by a suspected sarin attack that killed 1,400 people in Eastern Ghouta.

But OPCW investigators said they believed that orders for the 2018 Saraqeb attack must have come from above, and there was no indication "rogue elements or individuals" were responsible.

"The IIT obtained information from various sources suggesting that, for chemical weapons to be used in the manner described above, orders would be required," the report on the attack said.

While it had not identified a "specific chain of command", the Syrian military general command appeared to have "delegated decisions on the use of chlorine to "operational level commanders", the OPCW said.

OPCW member states will vote later this month on whether to impose sanctions on Syria, including the suspension of its voting rights in the organisation, over failure to comply with its rules.