The land-based defensive missile systems were set up in Fiery Cross Reef, Subi Reef and Mischief Reef on the Spratly Islands within the past 30 days, anonymous sources told CNBC.
Additional military equipment was reportedly spotted on satellite images of the nearby Woody Island, the largest of the Paracel Islands hosting Chinese military headquarters.
An earlier report by the Asia Times said that Beijing was establishing another base in Sanya, a city on the southern edge of China's Hainan island in the South China Sea for the deployment of manned and unmanned submersible vehicles. Meanwhile, The Chinese People's Daily outlet has reported that workers are set to complete a new research center in Sanya for maritime exploration and data collection by 2019.