The Chinese military said an American naval ship “illegally intruded” on Monday into waters near a disputed South China Sea atoll that has recently seen several maritime confrontations.

A Chinese naval force was mobilised to track the USS Gabrielle Giffords during the operation, according to a statement from the People's Liberation Army Southern Theatre.

According to the Chinese military, the US ship moved into waters adjacent to what China calls the Renai Reef, also known as Second Thomas Shoal, a part of the Nansha, or Spratly Islands.

"The US seriously undermined regional peace and stability," a spokesperson said in a statement, adding that the US violated China's sovereignty.

"Troops in the theatre of command maintain a high state of alert at all times, resolutely defending national sovereignty and security."

The US Navy said the USS Gabrielle Giffords was conducting routine operations in international waters in the South China Sea, consistent with international law. (Agencies)