WARNING: Viewers may find some images in this report disturbing.<br /><br />The US has said that Syria has probably used chemical weapons against rebel forces on a "small scale," but emphasised that intelligence services were still not 100 percent sure.<br /><br />US spy agencies have investigated reports from Syrian opposition groups that President Bashar al-Assad's forces have used sarin gas on at least two occasions during the two-year-old conflict.<br /><br />Al Jazeera's Peter Sharp reports.
