SANA news agency quoted a military source as saying the attacks wounded four soldiers.
The global chemical weapons watchdog has “reasonable grounds to believe” that Syria’s air force dropped a chlorine bomb on a residential neighbourhood in the rebel-controlled Idlib region.
The new report by the Organisation for the Prohibition of Chemical Weapons (OPCW) investigative arm said on Monday no one was killed when the cylinder of chlorine gas, delivered in a barrel bomb, hit the al-Talil neighbourhood in the city of Saraqeb in February 2018.
However, a dozen people were treated for symptoms consistent with chemical poisoning, including nausea, eye irritation, shortness of breath, coughing and wheezing, the report said.
“The cylinder ruptured and released chlorine over a large area, affecting 12 named individuals,” the watchdog said in a statement. Those affected all survived, it added.
There was no immediate comment from the Syrian government on Monday.
Syria and its military ally Russia have consistently denied using chemical weapons during President Bashar al-Assad’s decade-old conflict with rebel forces, saying any such attacks were staged by opponents to make Damascus look like the culprit.
Chlorine is not an internationally banned toxin, but the use of any chemical substance in armed conflict is banned under the 1997 Chemical Weapons Convention, the implementation of which is overseen by the OPCW watchdog based in The Hague.
A crackdown on pro-democracy demonstrators by al-Assad in 2011 mushroomed into civil war, with Russia and Iran supporting his government and the United States, Turkey, and some Arab adversaries of Damascus backing some of the many rebel groups.
As part of the investigation, experts interviewed witnesses, analysed samples and remnants collected from the town, reviewed symptoms reported by casualties and studied satellite imagery and modelled gas dispersion patterns.
The OPCW cannot hold individuals criminally responsible for attacks. The report will be shared with the organisation’s member states and the United Nations.
In April 2020, the OPCW’s Investigation and Identification Team (IIT) concluded that Syrian warplanes and a helicopter dropped bombs containing chlorine and sarin nerve gas on a village in Syria’s Hama region in March 2017.
The latest report by the IIT also implicated Syrian government forces. It concluded “there were reasonable grounds to believe that at least one cylinder filled with chlorine was dropped from a helicopter of the Syrian Arab Air Forces, belonging to the Tiger Forces”.
The Tiger Forces are an elite Syrian military unit generally used in offensive operations in the war, which has largely subsided after al-Assad wrested back most territory with crucial Russian and Iranian support.
“All elements indicated the presence of Tiger Forces in the vicinity of Saraqeb. They found that a helicopter was just flying above the bombed area at the moment of the gas release,” a summary of the OPCW report said.
It said samples collected from the scene were examined and other possible means of chlorine contamination considered, but the OPCW team said nothing was found to indicate the incident was staged by al-Assad’s adversaries.
The team identified individuals believed to be involved in the alleged attack but did not release names.
Between 2015 and 2017, a joint United Nations-OPCW team known as the Joint Investigative Mechanism (JIM) found that Syrian government troops used the nerve agent sarin and chlorine barrel bombs on several occasions, while ISIL (ISIS) fighters were found to have used mustard gas.