BEIJING: For months, China’s visible construction of artificial islands and military facilities in the West Philippine Sea (South China Sea) has alarmed US officials and many of China’s neighbors. What is happening under the water is also worrisome, say several defense and security analysts.

China has a growing fleet of nuclear submarines armed with ballistic missiles. The expansion of its claim on the West Philippine Sea may be intended to create a deep-water sanctuary--known in military parlance as a “bastion”--where its submarine fleet could avoid detection.