US destroyer in South China Sea
US Navy's guided-missile destroyer sails through the South China Sea near artificially made islands which are claimed by Beijing US Navy handout via Reuters

Ignoring Beijing's warning, the USS Lassen sailed through the territories of the South China Sea which are unilaterally claimed by China. In a direct challenge to China, the US warship navigated near man-made islands built by Beijing.

"The whole point of freedom of navigation in international waters is that it's international waters. You don't need to consult with anybody. That's the idea," said State Department spokesperson John Kirby.

The US Navy's guided-missile destroyer was sailing within 12 nautical miles (22.2km) of Subi and Mischief reefs in the Spratly Islands on Tuesday (27 October) morning local time. The region is widely considered as international waters but Beijing claims large parts of the South China Sea. Many nations including Vietnam, Taiwan, the Philippines and Malaysia are entangled in the messy territorial claims in the region.

The US operation, dubbed as a transit mission, reportedly has the blessings of President Barack Obama and was completed within a few hours. Just before the confirmation of Lassen's cruising in the South China Sea waters, Chinese Foreign Minister Wang Yi warned: "We are checking out the matter. If it is true, we advise the US to think twice before its action, not to act in an imprudent way and not to make trouble out of nothing."

The Chinese embassy in Washington reacted strongly to the US move with spokesperson Zhu Haiquan saying: "Freedom of navigation and overflight should not be used as excuse to flex muscle and undermine other countries' sovereignty and security. We urge the United States to refrain from saying or doing anything provocative and act responsibly in maintaining regional peace and stability."

According to Reuters, which first reported about the events, a senior Obama administration official said more such patrols are expected to take place in the coming weeks. Since 2014, China has stepped up its reclamation activity in the area prompting the US and other nations to intensify counter-measures. This has even led to confrontation between US forces and the Chinese navy in the past.