Beijing: China "really needs" its defences in the South China Sea in the face of a militarisation process being pushed by the United States, and can deploy whatever equipment it wants on its own soil, China's Defence Ministry said on Thursday.

China and the United States have sparred repeatedly over the past week following reports China is deploying advanced missiles, fighters and radar equipment on islands in the South China Sea, especially on Woody Island in the Paracels.

Annotated satellite images of Woody Island, the largest of the Paracel Islands in the South China Sea. A US official confirmed that China has placed a surface-to-air missile system on Woody Island. Credit:AP

The United States has accused China of militarising the disputed waters. Beijing, for its part, has been angered by "freedom of navigation" air and sea patrols the United States has conducted near islands China claims in the South China Sea.