The Chinese Defense Ministry is accusing the United States of carrying out "a serious military provocation," after the US flew two bombers over an artificial island in the South China Sea.
The US claims that the flyover was a mistake, and resulted from the pilots veering off course.
China insists that it has sovereignty over almost all islands, reefs and other projections in the area, and says that it will do whatever it must in order to maintain control. Other countries have expressed concern that the sites are either attempts at Chinese expansionism or are being used as military platforms.
The US, in particular, has denounced China's expansions. It claims that Beijing is threatening free passage through the area that hosts a third of the world's oil traffic.