The United Nations inspectors have confirmed the use of chemical weapons in an attack near the Syrian capital last month.
According to the inspectors' report, expected to be released by UN Secretary-General Ban Ki-moon later on Monday, environmental, chemical and medical samples show that surface-to-surface rockets containing the nerve agent sarin were used in the Ghouta suburb of Damascus on August 21.
"The conclusion is that chemical weapons have been used in the ongoing conflict between the parties in the Syrian Arab Republic ... against civilians, including children, on a relatively large scale," says the report by UN inspectors.
The detail was inadvertently leaked when the first page of the report was included in an official picture of head of the UN investigators, Ake Sellstrom, showing him handing over the report to the UN chief.
Ban was scheduled to brief the Security Council on the report on Monday. He is then expected to address the media.
Hundreds of people were killed and scores of others were injured in a chemical attack in the Damascus suburbs of Ain Tarma, Zamalka and Jobar on August 21.
The militants operating inside Syria and the foreign-backed Syrian opposition claimed that the deadly attack was carried out by the army.
Damascus, however, has strongly denied the accusation, saying it was a false-flag operation carried out by the Takfiri groups in a bid to draw in foreign military intervention.
Following the chemical attack, the US called for punitive military action against Damascus. The Syrian government averted possible US aggression by accepting a Russian plan to put its chemical arsenal under international control and then have them destroyed.