Fiery Cross Reef saw the most construction over the course of 2017, with work on buildings covering 27 acres, according to a recent report by the Asia Maritime Transparency Initiative. (Courtesy of AMTI)

Fiery Cross Reef saw the most construction over the course of 2017, with work on buildings covering 27 acres, according to a recent report by the Asia Maritime Transparency Initiative. (Courtesy of AMTI)

Subi Reef saw considerable building activity in 2017, with work on buildings covering about 24 acres, according to a recent report by the Asia Maritime Transparency Initiative. (Courtesy of AMTI)

In 2017, construction was undertaken on buildings covering 17 acres on Mischief Reef, according to a recent report by the Asia Maritime Transparency Initiative. (Courtesy of AMTI)

Beijing has continued island-building and militarization in the South China Sea, even as it enters negotiations with neighboring countries that also hold claims over disputed territory there.

“International attention has shifted away from the slow-moving crisis in the South China Sea over the course of 2017, but the situation on the water has not remained static,” the Asia Maritime Transparency Initiative said in a report released Thursday.

Satellite images recently released by the Washington-based think tank show that China has over the past year built additional infrastructure — including hangars, bunkers, missile shelters and radar — covering more than 70 acres on man-made islands in the Spratly and Paracel chains to equip larger outposts to be air and naval bases.

The U.S. and others have accused Beijing of further militarizing the region and altering geography to bolster its sweeping claims across a region where $5 trillion in global trade transits each year. China says the islands, which were built up using sand dredged from the sea bottom and then equipped with airstrips and military installations, are mainly for civilian purposes and to boost safety for fishing and maritime trade.

The report comes as China joins negotiations with Southeast Asian nations — including fellow island claimants Vietnam, the Philippines, Malaysia and Brunei — on a “code of conduct” for the South China Sea. Tensions over the issue with the United States, which occasionally conducts freedom-of-navigation patrols near those islands, have also eased, despite Washington’s criticism of Beijing’s conduct. Adm. Harry Harris — head of U.S. Pacific Command and a vocal critic of Beijing’s activities in the sea — has referred to the islands as China’s “great wall of sand.”

China’s land-reclamation efforts in the Spratly and Paracel chains appeared to be complete by mid-2017, the report said.

“But Beijing remains committed to advancing the next phase of its build-up — construction of the infrastructure necessary for fully-functioning air and naval bases on the larger outposts,” it added.

New facilities shown in the images “account for about 72 acres … of new real estate at Fiery Cross, Subi, and Mischief Reefs in the Spratlys, and North, Tree, and Triton Islands in the Paracels,” the report said.

In October and November, China deployed J-11B fighter jets and Y-8 transport aircraft to Woody Island, its military and administrative headquarters in the South China Sea, it added.

Marine Lt. Col. Christopher Logan, a Pentagon spokesman, said Thursday he could not comment in detail on U.S. assessments of the region but that “further militarization of outposts will only serve to raise tensions and create greater distrust among claimants.”

Brad Glosserman, a visiting professor at Tokyo’s Tama University, said the continued build-up is no surprise.

“This has been ongoing,” he said. “The fact that it’s publicly released means it has been known for a while.”

There was a lull in South China Sea tensions as Beijing sought stability during the Communist Party Congress in October and the U.S. focused on North Korea, Glosserman said.

However, tensions will likely build up again as America seeks changes to its trade relationship with China, he added.

The Associated Press contributed to this report.

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