China has quietly undertaken more construction and reclamation in the South China Sea, recent satellite images show, and is likely to more powerfully reassert its claims over the waterway soon, regional diplomats and military officers say.

With global attention focused on North Korea and Beijing engrossed in its Party Congress, tensions in the South China Sea have slipped from the headlines in recent months.

But with none of the underlying disputes resolved and new images reviewed by Reuters showing China continuing to develop facilities on North and Tree islands in the contested Paracel islands, experts say the vital trade route remains a global flashpoint.