BEIRUT -- The trajectory of the rockets that delivered the nerve agent sarin in last month's deadly attack is among the key evidence linking elite Syrian troops based in the mountains overlooking Damascus to the strike that killed hundreds of people, diplomats and human rights officials said Wednesday.
The Aug. 21 attack precipitated the crisis over Syria's chemical weapons. The U.S. threatened a military strike against Syria, which led to a plan negotiated by Moscow and Washington under which the regime of President Bashar Assad is to abandon its chemical weapons stockpile.
A UN report released Monday confirmed chemical weapons were used in the attack but did not ascribe blame.
The United States, Britain and France cited evidence in the report to declare Assad's government responsible. Russia called the report "one-sided" and said it has "serious reason to suggest that this was a provocation" by the rebels fighting the Assad regime in Syria's civil war.
The report, however, provided data that suggested the chemical-loaded rockets that hit two Damascus suburbs were fired from the northwest, indicating they came from nearby mountains where the Syrian military is known to have major bases.
Mount Qassioun, which overlooks Damascus, is home to one of Assad's three residences and is widely used by elite forces to shell suburbs of the capital. The powerful Republican Guard and army's Fourth Division, headed by Assad's younger brother, Maher, has bases there.
A senior UN diplomat, speaking on condition of anonymity because some of this material was from private meetings, said: "It was 100 per cent clear that the regime used chemical weapons."
The diplomat cited five key details, including the scale of the attack, the quality of the sarin, the type of rockets, the warheads used and the rockets' trajectory.
A Human Rights Watch report also said the presumed flight path of the rockets cited by the UN inspectors' report led back to a Republican Guard base in Mount Qassioun.
"Connecting the dots provided by these numbers allows us to see for ourselves where the rockets were likely launched from and who was responsible," said Josh Lyons, a satellite imagery analyst for the New York-based group. But, he added, the evidence was "not conclusive."
The HRW report matched what several experts concluded after reading the UN report. The UN inspectors were not instructed to assess which side was responsible for the attack.
"While the UN stuck within its mandate, it has provided enough data to provide an overwhelming case that this had to be government-sponsored," said Anthony Cordesman, national security expert at the Center for Strategic and International Studies.
The inspectors described the rockets used to disperse the sarin as a variant of an M14 artillery rocket, with either an original or an improvised warhead, which the rebels are not known to have. There is no conceivable way to prove the rebels could not have got them, Cordesman said, but he added the modification of the rockets pointed to the regime.
The UN diplomat in New York pointed to citations in the UN report and a private briefing to the UN Security Council by chief inspector Ake Sellstrom that reveal the scale of the attack: The seven rockets examined had a total payload of about 350 litres of sarin, including sophisticated stabilizing elements that match those known to be in the Syrian stockpile.
This makes it "virtually impossible" it came from any source other than the Syrian government, the diplomat said, adding there were likely other rockets used that the inspectors couldn't get to.
In the contested northern city of Aleppo, a group of volunteers learned how to deal with chemical weapons attacks in a drill inside a school. Three gas masks and 24 protective suits were given to them after rebels gained control of a military base belonging to forces loyal to Assad. The volunteers are distributing leaflets to residents on how to react to an attack.
-- The Associated Press