UNITED NATIONS - Chemical weapons were likely used in five out of seven attacks investigated by UN experts in Syria, where a 2 1/2-year civil war has killed more than 100,000 people, according to the final report of a UN inquiry published on Thursday.

UN investigators said the deadly nerve agent sarin was likely used in four incidents, in one case on a large scale.

The report noted that in several cases the victims included government soldiers and civilians, though it was not always possible to establish with certainty any direct links between the attacks, the victims and the alleged sites of the incidents.

"The United Nations Mission concludes that chemical weapons have been used in the ongoing conflict between the parties in the Syrian Arab Republic," the final report by chief UN investigator Ake Sellstrom said.

Syria's UN Ambassador Bashar Ja'afari and the opposition Syrian National Coalition did immediately comment on the 82-page report.

The investigation found likely use of chemical weapons in Khan al-Assal, near the northern city of Aleppo, in March; in Saraqeb, near the northern city of Idlib, in April; and in Jobar and Ashrafiat Sahnaya, near Damascus, in August.

As initially reported by Sellstrom in September, there was "clear and convincing" evidence that sarin was used on a large-scale against civilians in the rebel-held Damascus suburb of Ghouta on August 21, killing hundreds of people.

In the final report on Thursday, the experts said sarin had likely also been used on a small-scale in Jobar, Saraqeb and Ashrafiat Sahnaya.

The inquiry was only looking at whether chemical weapons were used, not who used them. The Syrian government and the opposition have accused each other of using chemical weapons, and both have denied it.