The US navy patrol near the Paracel Islands was "motivated by a desire to see the world in chaos," the Chinese Defense Ministry said in a Friday statement.

"This is serious illegal behavior, and is intentionally provocative behavior," the Beijing officials said, adding they had raised "serious" complaints with the US.

Earlier on Friday, US officials confirmed that their guided-missile destroyer USS Decatur conducted a so-called "freedom of navigation" exercise in the Chinese-claimed waters, aimed at challenging Beijing's territorial ambitions.

The destroyer "conducted this transit in a routine, lawful manner without ship escorts and without incident," according to the Pentagon. The White House also confirmed the maneuver, which follows two similar South China Sea patrols earlier this year.

"This operation demonstrated that coastal states may not unlawfully restrict the navigation rights, freedoms and lawful uses of the sea that the United States and all states are entitled to exercise under international law," White House spokesman Josh Earnest told reporters.

Defending national security

The incident prompted two Chinese warships to warn the US vessel to leave the Chinese "territorial waters," officials said. Officials urged the US to "not keep repeating the same mistakes" in the Friday statement.

"The Chinese military will increase its air and maritime patrol efforts in accordance with need, strengthen defense ability building in all areas, and resolutely defend national sovereignty and security," they said.

Beijing scrambled fighter jets in response to the previous perceived intrusion in May.

China claims nearly all of the South China Sea and the key military and trade routes in the area. Several other countries, including Malaysia, Vietnam and the Philippines, dispute Beijing's assertions.

Show of force after Duterte breaks rank

Friday's operation comes after President Rodrigo Duterte of the Philippines dismissed an alliance with the US and hinted at closer ties with China, despite competing territorial claims. The move was hailed as a major positive development in Beijing.

According to the Chinese ministry, the Decatur patrol showed "that it is the United States which is the troublemaker when it comes to the stability of the South China Sea."

In turn, a Washington source quoted by Reuters said that the exercise was planned long before Duterte's remarks and his visit to Beijing this week. Previously, US officials said that they intended to carry on with the freedom-of-navigation exercises despite protests.

"The US Navy will continue to conduct routine and lawful operations around the world, including in the South China Sea, in order to protect the rights, freedoms and lawful uses of sea and airspace guaranteed to all. This will not change," Chief of Naval Operations Admiral John Richardson said during a visit to China in July.

dj/msh (Reuters, AFP)