The Pentagon released several videos on Thursday showing Chinese construction of man-made islands in the disputed waters of the South China Sea.
Since last year, China has been building previously submerged reefs into new islands by piling up massive amounts of sand from areas around the reef. The process allows China to create new landmasses, on which it can then build facilities. China claims these new islands as sovereign territory, which the U.S. rejects.
The Pentagon's footage was shot on Wednesday by a P-8A Poseidon U.S. Navy surveillance plane flying around the Spratly Islands, and depicts concrete manufacturing facilities and a runway being constructed.
The surveillance flight led to a public spat between China and the U.S., and the footage released Thursday also registered a message from the Chinese navy in the surveillance plane's cockpit, warning the Americans to leave the area.
CNN, which had a crew on board, reported the message as saying, "This is the Chinese navy ... This is the Chinese navy ... Please go away ... to avoid misunderstanding."
Thursday's video release is part of a recent effort by the U.S. military to openly challenge what it sees as China's growing attempts to exert influence in the region.
China has been locked in a dispute with several countries, including the Philippines, Taiwan and Malaysia, over territorial control of areas in the South China Sea. The region is home to important commercial shipping routes and is believed to contain significant resources. Beijing claims much of the waters and the island groups within them, and some governments fear the Chinese government aims to use the new islands to stake claims of sovereignty over the contested territory.
The dispute is a continuing source of security concerns for China's neighbors, and the United States has warned China that its moves in the South China Sea risk destabilizing the region.
"As China seeks to make sovereign land out of sandcastles and redraw maritime boundaries, it is eroding regional trust and undermining investor confidence," U.S. Deputy Secretary of State Antony Blinken said at a press conference in Jakarta on Wednesday.
Several days before the surveillance flight, China's Foreign Minister, Wang Yi, claimed that the construction of landmasses in the South China Sea “is something that falls fully within the scope of China’s sovereignty."
China's Foreign Ministry spokesman Hong Lei condemned the U.S. flyovers on Friday, saying, "Such action is likely to cause an accident, it is very irresponsible and dangerous and detrimental to regional peace and stability."