Careful not to blame either side for a deadly chemical weapon attack, UN inspectors reported that rockets loaded with the nerve agent sarin had been fired from an area where Syria's military has bases, but said the evidence could have been manipulated in the rebel-controlled stricken neighbourhoods.
The US, Britain and France jumped on evidence in Monday's report - especially the type of rockets, the composition of the sarin agent, and trajectory of the missiles - to declare that president Bashar Assad's government was responsible.
Russia, Syria's closest ally, called the investigators' findings "deeply disturbing", but said it was too early to draw conclusions. The Syrian government's claims that opposition forces were responsible for the attack "cannot be simply shrugged off", Russian ambassador Vitaly Churkin insisted.
The conclusions represented the first official confirmation by impartial scientific experts that chemical weapons were used in Syria's civil war, but the inspectors' limited mandate barred them from identifying who was responsible for the August 21 attack.
"This is a war crime," UN secretary-general Ban Ki-moon told the Security Council when he presented the report. "The results are overwhelming and indisputable. The facts speak for themselves." He called it "the most significant confirmed use of chemical weapons against civilians since Saddam Hussein used them" in Halabja, Iran, in 1988, and "the worst use of weapons of mass destruction in the 21st century".
The deep division between Western backers of rebels seeking to overthrow Assad and Russian and Chinese supporters of the regime has paralysed the UN Security Council since the Syrian conflict began more than two years ago. Even though the US and Russia agreed on Saturday on the framework to put Syria's chemical weapons stockpile under international control for future destruction, their diplomats were at odds on Monday over a new Security Council resolution that would make the deal legally binding - and whether there should be a reference to possible military enforcement if Syria does not comply.
After months of negotiations, the UN inspectors went to Syria to visit the sites of three alleged chemical attacks earlier this year and were in the capital Damascus on August 21 when reports and videos began surfacing of a shelling attack in which victims experienced shortness of breath, disorientation, blurred vision, nausea, vomiting, weakness and a loss of consciousness. They finally gained access to three towns where that attack occurred, and on one occasion their convoy was hit by sniper fire, but the inspectors were nonetheless able to collect a large amount of material and talk to survivors and witnesses.
"The environmental, chemical and medical samples we have collected provide clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used ... in the Ghouta area of Damascus," their report said. "The conclusion is that chemical weapons have been used in the ongoing conflict between the parties in the Syrian Arab Republic, also against civilians, including children, on a relatively large scale. This result leaves us with the deepest concern."
The rebels and their Western and Arab supporters have blamed Assad's regime for the attack in the rebel-controlled area of Ghouta. The Syrian government insists the attack was carried out by rebels. The UN report mentions the Ghouta areas of Ein Tarma, Moadamiyeh and Zamalka, all of which were featured in videos of victims that emerged after the attack. The UN report did not mention how many people were killed in the August 21 attack. The US says more than 1,400, but other death toll estimates have been far lower.
The Syrian National Coalition - the main umbrella opposition group - welcomed the inspectors' report and urged the Security Council to hold the Assad regime responsible for the attack and refer the Syrian government to the International Criminal Court for prosecution. General Salim Idris, head of the rebel Free Syrian Army, said in an interview on the PBS NewsHour that the inspectors' report makes "very clear that there's a war crime". He said the Syrian people "are very frustrated because of what's going on and because the international community is not caring any more about the victims".