UN inspectors have confirmed that chemical weapons have been used in the Syrian conflict, definitely in a widely publicised August attack near Damascus and probably in four other locations between March and late August, Belfast Telegraph said.

The report by UN chemical weapons experts, led by Swedish professor Ake Sellstrom, examined seven alleged chemical weapons attacks and said it lacked information to corroborate the allegations at two locations.

The inspectors' limited mandate barred them from identifying whether the government or opposition fighters were responsible for any of the attacks.

Prof Sellstrom issued an initial report on September 16 which concluded that evidence collected in the Ghouta area of Damascus following an August 21 attack provided "clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used". Graphic video footage showed dozens of people gasping for air and bodies lined up.

The report said evidence indicated chemical weapons were probably used in Khan al Assal, outside Aleppo, Jobar in Damascus's eastern suburbs, Saraqueb, near Idlib in the north west, and Ashrafiah Sahnaya, in the Damascus countryside.

The confirmed use of chemical weapons in Ghouta, and the threat of possible U.S. military action, led to a U.S.-Russian agreement to eliminate Syria's chemical weapons by mid-2014. The process of getting Syrian chemicals that can be used to make weapons out of the country is under way.

The experts said they collected "credible information that corroborates the allegations that chemical weapons were used in Khan al Assal on March 19, 2013 against soldiers and civilians".

But the report said the release of chemical weapons at the site could not be independently verified because it lacked "primary information" on how the chemical agents were delivered and because environmental and medical samples were not scientifically collected, preserved and analysed.

The UN mission said it collected evidence "consistent with the probable use of chemical weapons in Jobar on August 24, 2013 on a relatively small scale against soldiers". But it said it lacked information on the delivery system and the chain of custody for samples, and therefore could not "establish the link between the victims, the alleged event and the alleged site".