The Collective Security Treaty Organization (CSTO) has commented on the tragic incident in Armenia as a result of the shooting down of a Russian helicopter by Azerbaijani servicemen.According to RIA Novosti, the organization's spokesman Vladimir Zainetdinov said."We express our serious concern over the incident and offer our condolences to the families and friends of the dead crew members. Let's wait for the results of the investigation to find out where the fire came from, "Zainetdinov said.Zainetdinov reminded that the CSTO has repeatedly called for a ceasefire.