The Syrian government’s chemical weapons stockpile has been linked for the first time by laboratory tests to the largest sarin nerve agent attack of the civil war, diplomats and scientists told Reuters, supporting Western claims that government forces under President Bashar al-Assad were behind the atrocity.
Laboratories working for the Organisation for the Prohibition of Chemical Weapons compared samples taken by a U.N. mission in the Damascus suburb of Ghouta after the Aug. 21, 2013 attack, when hundreds of civilians died of sarin gas poisoning, to chemicals handed over by Damascus for destruction in 2014.
The tests found “markers” in samples taken at Ghouta and at the sites of two other nerve agent attacks, in the towns of Khan Sheikhoun in Idlib governorate on April 4, 2017 and Khan al-Assal, Aleppo, in March 2013, two people involved in the process said.
“We compared Khan Sheikhoun, Khan al-Assal, Ghouta,” said one source who asked not to be named because of the sensitivity of the findings. “There were signatures in all three of them that matched.”
The same test results were the basis for a report by the OPCW-United Nations Joint Investigative Mechanism in October which said the Syrian government was responsible for the Khan Sheikhoun attack, which killed dozens.
The findings on Ghouta, whose details were confirmed to Reuters by two separate diplomatic sources, were not released in the October report to the U.N. Security Council because they were not part of the team’s mandate.
They will nonetheless bolster claims by the United States, Britain and other Western powers that Assad’s government still possesses and uses banned munitions in violation of several Security Council resolutions and the Chemical Weapons Convention.
The OPCW declined to comment. Syria has repeatedly denied using chemical weapons in the conflict now in its seventh year and has blamed the chemical attacks in the rebel-held territory of Ghouta on the insurgents themselves.
Russia has also denied that Syrian government forces have carried out chemical attacks and has questioned the reliability of the OCPW inquiries. Officials in Moscow have said the rebels staged the attacks to discredit the Assad government and whip up international condemnation.
Under a U.S.-Russian deal after the Ghouta attack in 2013, Damascus joined the OPCW and agreed to permanently eliminate its chemical weapons program, including destroying a 1,300-tonne stockpile of industrial precursors that has now been linked to the Ghouta attack.
But inspectors have found proof of an ongoing chemical weapons program in Syria, including the systematic use of chlorine barrel bombs and sarin, which they say was ordered at the highest levels of government.
The sarin attack on Khan Sheikhoun in April last year prompted U.S. President Donald Trump to order a missile strike against the Shayrat air base, from which the Syrian operation is said to have been launched.
Diplomatic and scientific sources said efforts by Syria and Russia to discredit the U.N.-OPCW tests establishing a connection to Ghouta have so far come up with nothing.
Russia’s blocking of resolutions at the Security Council seeking accountability for war crimes in Syria gained new relevance when Russia stationed its aircraft at Shayrat in 2015.
Washington fired missiles at Shayrat in April 2017, saying the Syrian air force used it to stage the Khan Sheikhoun sarin attack on April 4 a few days earlier, killing more than 80 people.
No Russian military assets are believed to have been hit, but Moscow warned at the time it could have serious consequences.
In June, the Pentagon said it had seen what appeared to be preparations for another chemical attack at the same airfield, prompting Russia to say it would respond proportionately if Washington took pre-emptive measures against Syrian forces there.