The Asia Maritime Transparency Initiative (AMTI), which falls under Washington’s Center for Strategic and International Studies, reports that satellite images show new Chinese military facilities being built on islands in the contested waters of the South China Sea.

According to their report, missile shelters and radar and communications facilities are currently under construction on Fiery Cross, Mischief, and Subi Reefs in the Spratly Islands.

The United States has repeatedly criticized China’s efforts to build and militarize islands in the heavily trafficked waterway, accusing the Chinese of attempting to enforce their contested claims over the region.  The South China Sea is among the most heavily commercial trafficked bodies of water on the planet, with an estimated one-third of global commerce crossing it per year.

The South China Sea is also said to be rich in natural resources, including fish and natural gas, prompting nearly every other nation bordering the sea to lay claims to portions China purports to control, despite being hundreds of miles, in many cases, from Chinese shores.

In order to enforce what the United States refers to as “freedom of navigation” for the international community, the U.S. Navy has sent ships through the region in close proximity to some of China’s islands.  Last month, a U.S. Navy vessel traveled to within 12 nautical miles of Mischief Reef, one of the islands being militarized by the Chinese, in the first act of such defiance since President Trump took office.

Despite satellite images showing their progress in developing military structures on these islands, China has publicly claimed that it is not, nor does it intend to, “militarize” the South China Sea, though they do stand by their claims that envelope nearly its entirety.  Brunei, Malaysia, the Philippines, Taiwan and Vietnam are among the nations with countering claims over portions of the waterway.

Four new missile structures on Fiery Cross Reef are visible in the satellite images, an increase from the eight already reported on the artificial island.  The Mischief and Subi have eight missile structures as well.  These missile structures are believed to be intended to house long-range surface to air missiles that would be capable of engaging aircraft over the sea.

On Mischief Reef, a large antennae array is also being constructed.  AMTI posits this array may be used to more closely monitor traffic throughout the South China Sea.  The antennae could be part of either a communications or radar system, but the think tank can’t specify further with any certainty – though a large dome built on Fiery Cross recently would seem to be indicative of a radar array.  There are two more domes currently under construction on Mischief Reef.