Tensions rise as US warship challenges China's claims in South China Sea.

China has warned of "serious consequences" after the US Navy sailed a destroyer around the disputed Paracel Islands in the South China Sea for the second day in a row, in a move Beijing claimed was a violation of its sovereignty and security. The US has challenged requirements from China, Taiwan, and Vietnam requiring either advance notification or permission before a military vessel sails by, calling it a "freedom of navigation operation." The US has no South China Sea claims itself, but has deployed Naval and Air Force assets for decades to patrol the strategic waterway.