The opposition Syrian National Coalition has denied Russian claims rebel fighters used chemical weapons in a deadly attack in March.

Moscow's United Nations envoy Vitaly Churkin says an inquiry has established that the rebels fired a missile containing the nerve agent sarin at the town of Khan al-Assal.The attack killed 26 people including 16 regime troops. Khalid Saleh, a spokesman for the coalition, has denied the charge, saying the United Nations should be allowed to investigate."The Free Syrian Army strongly condemns all usage of chemical weapons against a civilian population and denies Russia's allegations about the FSA using chemical weapons in Khan al-Assal, Aleppo," he said in a statement."Only the Assad regime has the know-how, capability and willingness to use these weapons.