Beijing (AFP) - Beijing "has the right" to declare an air defence identification zone over the South China Sea, it said on Wednesday as it stepped up denunciations of an international tribunal that ruled against its expansive claims in the strategic waters.

Whether Beijing set up such a zone -- which would require civilian aircraft to identify themselves to military controllers -- depended on "the level of threat we receive", said vice foreign minister Liu Zhenmin.

"Do not turn the South China Sea into a cradle of war," he told reporters, insisting: "China's aim is to turn the South China Sea into a sea of peace, friendship and cooperation".

China reasserted its claims to the area, which extend almost to the coasts of neighbouring states, after the Permanent Court of Arbitration (PCA) tribunal in The Hague backed the Philippines' case that there was no legal basis for them.