In a letter to the UN Secretary General Ban Ki-moon accompanying the fact-finding report, Ake Sellstrom, head of the mission responsible for probing the alleged use of chemical weapons in Damascus suburbs, said there was evidence that rockets and the nerve gas sarin were employed.
"On the basis of the evidence obtained during our investigation of the DamascusGhouta incident: the conclusion is that chemical weapons have been used, on a relatively large scale," Sellstrom said.
"In particular, the environmental, chemical and medical samples that we have collected provide a clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used in Ein Tarma, Moadamiyah and Zamalka in the Ghouta area of Damascus."
"This result leaves us with the deepest concern," the head of the UN probe mission said.
The mission was charged solely with the task of finding whether chemical weapons were used at Ghouta during Syria's civil war of more than two years but not who used them.