The USS Mustin American destroyer sailed within 12 nautical miles of Mischief Reef in the Spratly Islands on Friday, prompting an angry statement from Beijing claiming that China has “indisputable sovereignty” over the islands and accusing the United States of “harming regional peace and stability” with its patrols.

“All operations are designed in accordance with international law and demonstrate that the United States will fly, sail and operate wherever international law allows,” U.S. Pacific Fleet spokeswoman Lt. Cdr. Nicole Schwegman stated on Friday.

The Chinese Defense Ministry claimed that USS Mustin was “warned off” by two Chinese frigates as it approached.

“What the US is doing will damage the military-to-military relations and atmosphere. It could easily cause misjudgments and accidents at air or sea. This is a serious political and military provocation to China and the Chinese military is firmly objecting to this,” said Chinese Defense Ministry spokesman Ren Guoqiang.

“China holds indisputable sovereignty over the islands and their surrounding waters in the South China Sea,” Ren insisted. “By repeatedly sending military ships into these areas without authorization, the US has seriously harmed Chinese sovereignty and security, violated basic rules of international relations, and harmed regional peace and stability.”

China lodges similar complaints when the U.S. conducts “freedom of navigation” patrols through the area. Mischief Reef is one of several islands in the area that was artificially built up and equipped with military facilities by the Chinese over objections by the United States, international courts, and several other nations with claims in the region, including the Philippines, Taiwan, and Vietnam.

The Chinese Defense Ministry announced Friday it will conduct combat drills in the South China Sea in the near future, possibly including the nation’s only operational aircraft carrier, the Liaoning. The exercises were described as a routine part of the PLA Navy’s annual plan to “test and improve the troops’ training level and comprehensively enhance the capability to win.”