U.N. human rights investigators say chemical weapons used in two attacks in Syria last year appear to come from Syrian military stockpiles.
The team of independent experts, led by Brazilian Paulo Pinheiro, reported Wednesday the deadly nerve agent sarin was used in three incidents - the Damascus suburb of Ghouta on August 21, in Khan al-Assal, near Aleppo, in March and in Saraqeb, near the northern town of Idlib last April.
The report said in Ghouta significant quantities of sarin were used in a well-planned attack targeting civilian-inhabited areas, causing mass casualties.
It said evidence indicated the perpetrators "likely had access to the chemical weapons stockpile of the Syrian military, as well as the expertise and equipment necessary to manipulate safely large amount of chemical agents."
Pinheiro said his team is investigating up to 20 incidents in which chemical weapons were used in Syria.
Wednesday's report also concluded the five permanent U.N. Security Council members - Britain, China, France, Russia and the United States - have failed to act on all of Syria's "grave violations" that threaten international peace and security.
Syria's main allies, Russia and China, have repeatedly blocked Western proposals before the Security Council, the most powerful U.N. arm.
The report recommended that countries with influence in Syria, particularly the permanent Security Council members, exert more pressure to end the violence and find a political solution to the Syrian crisis.
The Syrian government and the opposition have accused each other of using chemical weapons, banned under international law, and both have denied it.
President Bashar al-Assad agreed to destroy his chemical weapons following global outrage over the sarin gas attack at Ghouta in August, the world's deadliest chemical attack in 25 years.
It drew a U.S. threat of military strikes that was averted after Mr. Assad pledged to give up his chemical arms.