Satellite photos show that China has erected reinforced aircraft hangars on a group of reefs that it built up into islands the disputed South China Sea, according to a Washington, DC defense think tank.

The images came out a month after an international court in The Hague ruled against China's sweeping claims in the resource-rich region, through which some US$5 Trillion in shipping traffic passes through every year, mostly because the islands are hundreds of kilometers beyond China's internationally-recognized maritime boundaries.  But Beijing has rejected that ruling, despite already being member of a treaty making it legally binding.

"Except for a brief visit by a military transport plane to Fiery Cross Reef earlier this year, there is no evidence that Beijing has deployed military aircraft to these outposts. But the rapid construction of reinforced hangars at all three features indicates that this is likely to change," says a report from the Center for Strategic and International Studies (CSIS).  The group adds that that the new structures are large enough to handle any aircraft in the Chinese Air Force.  The US and others have repeatedly urged Beijing not to militarize these holdings, and President Xi Jinping during a visit to the White House last September claimed that China's intentions were peaceful.  Oh well.

"They are far thicker than you would build for any civilian purpose," said Gregory Poling, director of CSIS's Asia Maritime Transparency Initiative.  "They're reinforced to take a strike."

Meanwhile, Japan warned China on Tuesday that ties were "deteriorating markedly" over China's menacing behavior towards the Senkaku Islands in the East China Sea which have been under Japanese control for more than a century but which Beijing also claims (since the 1970s).  Foreign Minister Fumio Kishida called in Chinese ambassador Cheng Yonghua and accused Beijing of trying to change the status quo unilaterally.  Tensions between Asia's two largest economies have risen since China sent a phalanx of ships - including armed Coast Guard vessels - through the Japanese waters last week.