Cambodia has outlawed sand exports from a coastal region where it has been primarily funnelled in huge quantities to Singapore, a move met with scepticism from activists who said previous bans on the destructive industry had failed to take root. Environmental groups have long accused Cambodia of running damaging and corrupt sand dredging operations along the southwest coast and the Mekong river. Most of the sand has been shipped to Singapore to fuel the wealthy city-state's rapid expansion -- a resource plunder that activists say has devastated local Cambodian communities and ecosystems.